Vision correction system and method, light field display and light field shaping layer and alignment therefor

ABSTRACT

Described are various embodiments of a digital display device for use by a user having reduced visual acuity. In one embodiment, the device comprises: a digital display medium comprising an array of pixels and operable to render a pixelated image accordingly; a light field shaping layer defined by an array of light field shaping elements and disposed relative to said digital display so to align each of said light field shaping elements with a corresponding set of said pixels to shape a light field emanating therefrom and thereby at least partially govern a projection thereof from said display medium toward the user; and a hardware processor operable on pixel data for the image such that said processed image is rendered to at least partially compensate for the user’s reduced visual acuity.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Pat. App. No. 17/661,675 filed May 2, 2022, which is a continuation of U.S. Pat. App. No. 17/016,238 filed Sep. 9, 2020, which is a continuation-in-part of international application no. PCT/IB2019/051896 filed Mar. 8, 2019, a continuation-in-part of international application no. PCT/IB2019/051893 filed Mar. 8, 2019, and a continuation-in-part of international application no. PCT/IB2019/051871 filed Mar. 8, 2019. PCT/IB2019/051896 is a continuation-in-part of U.S. Pat. App. No. 16/259,845 filed Jan. 28, 2019. PCT/IB2019/051871 is a continuation-in-part of U.S. Pat. App. No. 16/259,845 filed Jan. 28, 2019. PCT/IB2019/051893 is a continuation-in-part of U.S. Pat. App. No. 16/259,845 filed Jan. 28, 2019. The entire disclosures of each of which is hereby incorporated by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to digital displays, and in particular, to a vision correction system and method, light field display and light field shaping layer therefor.

BACKGROUND

Individuals routinely wear corrective lenses to accommodate for reduced vision acuity in consuming images and/or information rendered, for example, on digital displays provided, for example, in day-to-day electronic devices such as smartphones, smart watches, electronic readers, tablets, laptop computers and the like, but also provided as part of vehicular dashboard displays and entertainment systems, to name a few examples. The use of bifocals or progresses corrective lenses is also commonplace for individuals suffering from near and far sightedness.

The operating systems of current electronic devices having graphical displays offer certain “Accessibility” features built into the software of the device to attempt to provide users with reduced vision the ability to read and view content on the electronic device. Specifically, current accessibility options include the ability to invert images, increase the image size, adjust brightness and contrast settings, bold text, view the device display only in grey, and for those with legal blindness, the use of speech technology. These techniques focus on the limited ability of software to manipulate display images through conventional image manipulation, with limited success.

Light field displays using lenslet arrays or parallax barriers have been proposed for correcting such visual aberrations. For a thorough review of Autostereoscopic or light field displays, Halle M. (Halle, M., “Autostereoscopic displays and computer graphics” ACM SIGGRAPH, 31(2), pp. 58-62, 1997) gives an overview of the various ways to build a glasses-free 3D display, including but not limited to parallax barriers, lenticular sheets, microlens arrays, holograms, and volumetric displays, for example. Moreover, the reader is also directed to another article by Masia et al. (Masia B., Wetzstein G., Didyk P. and Gutierrez, “A survey on computational displays: Pushing the boundaries of optics, computation and perception”, Computer & Graphics 37 (2013), 1012-1038), which also provides a good review of computational displays, notably light field displays at section 7.2 and vision correcting light field displays at section 7.4.

A first example of using light field displays to correct visual aberrations has since been proposed by Pamplona et al. (PAMPLONA, V., OLIVEIRA, M., ALIAGA, D., AND RASKAR, R.2012. “Tailored displays to compensate for visual aberrations.” ACM Trans. Graph. (SIGGRAPH) 31.). Unfortunately, conventional light field displays as used by Pamplona et al. are subject to a spatio-angular resolution trade-off; that is, an increased angular resolution decreases the spatial resolution. Hence, the viewer sees a sharp image but at the expense of a significantly lower resolution than that of the screen. To mitigate this effect, Huang et al. (see, HUANG, F.-C., AND BARSKY, B. 2011. A framework for aberration compensated displays. Tech. Rep. UCB/EECS-2011-162, University of California, Berkeley, December; and HUANG, F.-C., LANMAN, D., BARSKY, B. A., AND RASKAR, R. 2012. Correcting for optical aberrations using multi layer displays. ACM Trans. Graph. (SiGGRAPH Asia) 31, 6, 185:1-185:12. proposed the use of multilayer display designs together with prefiltering. The combination of prefiltering and these particular optical setups, however, significantly reduces the contrast of the resulting image.

Moreover, in U.S. Pat. Application Publication No. 2016/0042501 and Fu-Chung Huang, Gordon Wetzstein, Brian A. Barsky, and Ramesh Raskar. “Eyeglasses-free Display: Towards Correcting Visual Aberrations with Computational Light Field Displays”. ACM Transaction on Graphics, xx:0, August 2014, the entire contents of each of which are hereby incorporated herein by reference, the combination of viewer-adaptive pre-filtering with off-the-shelf parallax barriers has been proposed to increase contrast and resolution, at the expense however, of computation time and power.

Another example includes the display of Wetzstein et al. (Wetzstein, G. et al., “Tensor Displays: Compressive Light Field Synthesis using Multilayer Displays with Directional Backlighting”, https://web.media.mit.edu/~gordonw/TensorDisplays/TensorDisplays.pdf) which discloses a glass-free 3D display comprising a stack of time-multiplexed, light-attenuating layers illuminated by uniform or directional backlighting. However, the layered architecture may cause a range of artifacts including Moiré effects, color-channel crosstalk, interreflections, and dimming due to the layered color filter array. Similarly, Agus et al. (AGUS M. et al., “GPU Accelerated Direct Volume Rendering on an Interactive Light Field Display”, EUROGRAPHICS 2008, Volume 27, Number 2, 2008) discloses a GPU accelerated volume ray casting system interactively driving a multi-user light field display. The display, produced by the Holographika company, uses an array of specially arranged projectors and a holographic screen to provide glass-free 3D images. However, the display only provides a parallax effect in the horizontal orientation as having parallax in both vertical and horizontal orientations would be too computationally intensive. Finally, the FOVI3D company (http://on-demand.gputechconf.com/gtc/2018/presentation/s8461-extreme-multi-view-rendering-for -light-field-displays.pdf) provides light field displays wherein the rendering pipeline is a replacement for OpenGL which transports a section of the 3D geometry for further processing within the display itself. This extra processing is possible because the display is integrated into a bulky table-like device. However, the extra space required by the bulky frame and extensive computation power is unavailable when seeking to implement computationally approachable vision correction applications on portable devices, vehicular dashboards, smartphones, smart watches or other such consumer products and/or applications.

This background information is provided to reveal information believed by the applicant to be of possible relevance. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art.

SUMMARY

The following presents a simplified summary of the general inventive concept(s) described herein to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to restrict key or critical elements of the invention or to delineate the scope of the invention beyond that which is explicitly or implicitly described by the following description and claims.

A need exists for a vision correction system and method, light field display and optical element array therefor, that overcome some of the drawbacks of known techniques, or at least, provide a useful alternative thereto. Some aspects of the disclosure provide embodiments of such systems, methods, displays and optical element arrays, such as microlens arrays, or again, using subpixel rendering, for example.

In accordance with one aspect, there is provided a digital display device to render an image for viewing by a viewer having reduced visual acuity, the device comprising: a digital display medium comprising an array of pixels and operable to render a pixelated image accordingly; a light field shaping layer (LFSL) defined by an array of LFSL elements and disposed relative to said digital display medium so to dispose each of said LFSL elements over an underlying set of said pixels to shape a light field emanating therefrom and thereby at least partially govern a projection thereof from said display medium toward the viewer, wherein said LFSL is disposed relative to said digital display medium in geometric misalignment so to geometrically misalign said array of pixels and said array of LFSL elements; and a hardware processor operable on pixel data for the input image to output adjusted image pixel data to be rendered via said digital display medium and projected through said geometrically misaligned LFSL in accordance with said geometric misalignment so to produce a designated image perception adjustment to at least partially address the viewer’s reduced visual acuity.

In one embodiment, the hardware processor is operable to: digitally map the input image on an adjusted image plane designated to provide the user with the designated image perception adjustment; associate said adjusted image pixel data with at least some of said pixel sets according to said mapping and said geometric misalignment; and render said adjusted image pixel data via said pixel sets thereby rendering a perceptively adjusted version of the input image when viewed through said LFSL.

In one embodiment, the adjusted image plane is a virtual image plane virtually positioned relative to said digital display medium at a designated minimum viewing distance designated such that said perceptively adjusted version of the input image is adjusted to accommodate the viewer’s reduced visual acuity.

In one embodiment, the adjusted image plane is designated as a user retinal plane, wherein said mapping is implemented by scaling the input image on said retinal plane as a function of an input user eye focus aberration parameter.

In one embodiment, the hardware processor is operable to account for said geometric misalignment based on a stored mapping of each said LFSL element relative to said array of pixels.

In one embodiment, the array of pixels is angled or rotated relative to said array of LFSL elements.

In one embodiment, one of said array of pixels and said array of LFSL elements is defined by a square array whereas the other is defined by a hexagonal array.

In one embodiment, a pitch ratio between said array of pixels and said array of LFSL elements is designated as an irrational number.

In one embodiment, a pitch ratio between said array of pixels and said array of LFSL elements is designated so to define an array mismatch pattern that repeats on a periodic distance substantially equal to, or greater than a dimension of said digital display medium.

In one embodiment, the LFSL comprises at least one of a micro lens array, a parallax barrier, a diffractive light field barrier or a combination thereof.

In one embodiment, the LFSL comprises a microlens array having a focal length, and wherein said microlens array is disposed at a designated distance from said digital display that is shorter than said focal length so to produce a divergent light field therefrom.

In accordance with another aspect, there is provided a computer-implemented method, automatically implemented by one or more digital processors, to automatically adjust user perception of an input image to be rendered on a digital display medium via a set of pixels thereof to at least partially address a viewer’s reduced visual acuity, wherein the digital display medium has a light field shaping layer (LFSL) disposed thereon comprising an array of LFSL elements, wherein each of said LFSL elements is disposed over an underlying set of said pixels to shape a light field emanating therefrom and thereby at least partially govern a projection thereof from said display medium toward the viewer, the method comprising: digitally mapping the input image on an adjusted image plane designated to provide the user with a designated image perception adjustment; associating adjusted image pixel data with at least some of said pixel sets according to said mapping, and further according to a geometric misalignment of said array of LFSL elements and said array of pixels; and rendering said adjusted image pixel data via said pixel sets thereby rendering a perceptively adjusted version of the input image when viewed through said LFSL to at least partially address the viewer’s reduced visual acuity.

In one embodiment, the associating is implemented according to a stored mapping of each LFSL element relative to the array of pixels.

In one embodiment, the array of pixels is angled or rotated relative to the array of LFSL elements.

In one embodiment, one of the array of pixels and the array of LFSL elements is defined by a square array whereas the other is defined by a hexagonal array.

In one embodiment, a pitch ratio between the array of pixels and the array of LFSL elements is designated as an irrational number.

In one embodiment, a pitch ratio between the array of pixels and the array of LFSL elements is designated so to define an array mismatch pattern that repeats on a periodic distance substantially equal to, or greater than a dimension of the digital display medium.

In one embodiment, the adjusted image plane is a virtual image plane virtually positioned relative to the digital display at a designated minimum viewing distance designated such that said perceptively adjusted version of the input image is adjusted to accommodate the viewer’s reduced visual acuity.

In one embodiment, the adjusted image plane is designated as a user retinal plane, wherein said mapping is implemented by scaling the input image on said retinal plane as a function of an input user eye focus aberration parameter.

In accordance with another aspect, there is provided a non-transitory computer-readable medium having instructions stored thereon, to be automatically implemented by one or more digital processors, to automatically adjust user perception of an input image to be rendered by a digital display medium via a set of pixels thereof to at least partially address a viewer’s reduced visual acuity, wherein the digital display medium has a light field shaping layer (LFSL) disposed thereon comprising an array of LFSL elements, wherein each of said LFSL elements is disposed over an underlying set of said pixels to shape a light field emanating therefrom and thereby at least partially govern a projection thereof from the display medium toward the viewer, the instructions comprising instructions to: digitally map the input image on an adjusted image plane designated to provide the user with a designated image perception adjustment; associate adjusted image pixel data with at least some of said pixel sets according to said mapping, and further according to a geometric misalignment of the array of LFSL elements and the array of pixels; and render said adjusted image pixel data via said pixel sets thereby rendering a perceptively adjusted version of the input image when viewed through said LFSL to at least partially address the viewer’s reduced visual acuity.

In one embodiment, the associating is implemented according to a stored mapping of each LFSL element relative to the array of pixels.

In one embodiment, the array of pixels is angled or rotated relative to the array of LFSL elements.

In one embodiment, one of the array of pixels and the array of LFSL elements is defined by a square array whereas the other is defined by a hexagonal array.

In one embodiment, a pitch ratio between the array of pixels and the array of LFSL elements is designated as an irrational number.

In one embodiment, a pitch ratio between the array of pixels and the array of LFSL elements is designated so to define an array mismatch pattern that repeats on a periodic distance substantially equal to, or greater than a dimension of the digital display medium.

In one embodiment, the adjusted image plane is a virtual image plane virtually positioned relative to the digital display medium at a designated minimum viewing distance designated such that said perceptively adjusted version of the input image is adjusted to accommodate the viewer’s reduced visual acuity.

In one embodiment, the adjusted image plane is designated as a user retinal plane, wherein said mapping is implemented by scaling the input image on said retinal plane as a function of an input user eye focus aberration parameter.

In accordance with another aspect, there is provided a digital display device to render an image for viewing by a viewer having reduced visual acuity, the device comprising: a digital display medium comprising an array of pixels and operable to render a pixelated image accordingly, wherein each of said pixels comprises a combination of sub pixels geometrically disposed and associated therewith; a light field shaping layer (LFSL) defined by an array of LFSL elements and disposed relative to said digital display medium so to dispose each of said LFSL elements over an underlying set of said pixels to shape a light field emanating therefrom and thereby at least partially govern a projection thereof from said digital display medium toward the viewer; and a hardware processor operable on pixel data for the input image to output adjusted image pixel data to be rendered via said digital display medium through said LFSL in accordance with a stored alignment thereof so to produce a designated image perception adjustment to at least partially address the viewer’s reduced visual acuity, wherein said hardware processor is operable to calculate a light field component associated with at least some of said subpixels to output independently adjusted subpixel data values accordingly.

In one embodiment, the hardware processor is operable to: digitally map the input image on an adjusted image plane designated to provide the user with said designated image perception adjustment; associate said adjusted image pixel data with at least some of said pixel sets according to said mapping; and render said adjusted image pixel data via said pixel sets thereby rendering a perceptively adjusted version of the input image when viewed through said LFSL.

In one embodiment, the adjusted image plane is a virtual image plane virtually positioned relative to said digital display medium at a designated minimum viewing distance designated such that said perceptively adjusted version of the input image is adjusted to accommodate the viewer’s reduced visual acuity.

In one embodiment, the adjusted image plane is designated as a user retinal plane, wherein said mapping is implemented by scaling the input image on said retinal plane as a function of an input user eye focus aberration parameter.

In one embodiment, the adjusted image pixel data comprises an adjusted pixel colour computed so to manifest a corresponding adjusted image colour at a corresponding location on said adjusted image plane given said stored alignment.

In one embodiment, the adjusted subpixel data values comprise an adjusted image colour channel value.

In one embodiment, each of said subpixels is associated with a subpixel location on said digital display medium, and wherein said hardware processor is operable to calculate said light field component associated with a given subpixel based on said subpixel location thereof.

In one embodiment, each given pixel is associated with a given stored pixel location on said digital display medium, wherein each given subpixel for said given pixel is disposed at a respective stored subpixel offset relative to said given stored pixel location, and wherein said hardware processor is operable to calculate said light field component associated with said given subpixel by computationally offsetting a light field computation executed for said given pixel based on said given stored pixel location in accordance with said respective stored subpixel offset.

In one embodiment, each of said subpixels is associated with one of distinct colour channels, and wherein said hardware processor is operable to distinctly compute light field components for each of said distinct colour channels in a compressive light field optimization process.

In one embodiment, the LFSL comprises at least one of a micro lens array, a parallax barrier, a diffractive light field barrier or a combination thereof.

In accordance with another aspect, there is provided a computer-implemented method, automatically implemented by one or more digital processors, to automatically adjust user perception of an input image to be rendered on a digital display medium via a set of pixels thereof to at least partially address a viewer’s reduced visual acuity, wherein each of the pixels comprises a combination of sub pixels geometrically disposed and associated therewith, wherein the digital display medium has a light field shaping layer (LFSL) disposed thereon comprising an array of LFSL elements, the method comprising: digitally mapping the input image on an adjusted image plane designated to provide the user with a designated image perception adjustment; calculating a light field component associated with at least some of said subpixels to output independently adjusted subpixel data values according to said mapping and in accordance with a stored alignment of said LFSL elements relative to said pixels that at least partially governs a shaping of each said light field component; associating said independently adjusted subpixel data values with said subpixels; and rendering said independently adjusted subpixel data values thereby rendering a perceptively adjusted version of the input image when viewed through the LFSL to at least partially address the viewer’s reduced visual acuity.

In one embodiment, the adjusted image plane is a virtual image plane virtually positioned relative to said digital display medium at a designated minimum viewing distance designated such that said perceptively adjusted version of the input image is adjusted to accommodate the viewer’s reduced visual acuity.

In one embodiment, the adjusted image plane is designated as a user retinal plane, wherein said mapping is implemented by scaling the input image on said retinal plane as a function of an input user eye focus aberration parameter.

In one embodiment, the independently adjusted subpixel data values correspond to an adjusted pixel colour computed so to manifest a corresponding adjusted image colour at a corresponding location on said adjusted image plane given said stored alignment.

In one embodiment, the independently adjusted subpixel data values comprise an adjusted image colour channel value.

In one embodiment, each of said subpixels is associated with a subpixel location on said digital display medium, and wherein said calculating comprises calculating said light field component associated with a given subpixel based on said subpixel location thereof.

In one embodiment, each given pixel is associated with a given stored pixel location on said digital display medium, wherein each given subpixel for said given pixel is disposed at a respective stored subpixel offset relative to said given stored pixel location, and wherein said calculating comprises calculating said light field component associated with said given subpixel by computationally offsetting a light field computation executed for said given pixel based on said given stored pixel location in accordance with said respective stored subpixel offset.

In one embodiment, each of said subpixels is associated with one of distinct colour channels, and wherein calculating comprises distinctly computing light field components for each of said distinct colour channels in a compressive light field optimization process.

In accordance with another aspect, there is provided a non-transitory computer-readable medium having instructions stored thereon, to be automatically implemented by one or more digital processors, to automatically adjust user perception of an input image to be rendered by a digital display medium via a set of pixels thereof to at least partially address a viewer’s reduced visual acuity, wherein each of the pixels comprises a combination of subpixels geometrically disposed and associated therewith, wherein the digital display medium has a light field shaping layer (LFSL) disposed thereon comprising an array of LFSL elements, the instructions comprising instructions to: digitally map the input image on an adjusted image plane designated to provide the user with a designated image perception adjustment; calculate a light field component associated with at least some of said subpixels to output independently adjusted subpixel data values according to said map and in accordance with a stored alignment of said LFSL elements relative to said pixels that at least partially governs a shaping of each said light field component; associate said independently adjusted subpixel data values with said subpixels; and render said independently adjusted subpixel data values thereby rendering a perceptively adjusted version of the input image when viewed through the LFSL to at least partially address the viewer’s reduced visual acuity.

In one embodiment, the adjusted image plane is a virtual image plane virtually positioned relative to said digital display medium at a designated minimum viewing distance designated such that said perceptively adjusted version of the input image is adjusted to accommodate the viewer’s reduced visual acuity.

In one embodiment, the adjusted image plane is designated as a user retinal plane, wherein said mapping is implemented by scaling the input image on said retinal plane as a function of an input user eye focus aberration parameter.

In one embodiment, the independently adjusted subpixel data values correspond to an adjusted pixel colour computed so to manifest a corresponding adjusted image colour at a corresponding location on said adjusted image plane given said stored alignment.

In one embodiment, the independently adjusted subpixel data values comprise an adjusted image colour channel value.

In one embodiment, each of said subpixels is associated with a subpixel location on said digital display medium, and wherein said instructions to calculate comprise instructions to calculate said light field component associated with a given subpixel based on said subpixel location thereof.

In one embodiment, each given pixel is associated with a given stored pixel location on said digital display medium, wherein each given subpixel for said given pixel is disposed at a respective stored subpixel offset relative to said given stored pixel location, and wherein said instructions to calculate comprise instructions to calculate said light field component associated with said given subpixel by computationally offsetting a light field computation executed for said given pixel based on said given stored pixel location in accordance with said respective stored subpixel offset.

In one embodiment, each of said subpixels is associated with one of distinct colour channels, and wherein said instructions to calculate comprise instructions to distinctly compute light field components for each of said distinct colour channels in a compressive light field optimization process.

In accordance with another aspect, there is provided a digital display device to render an image for viewing by a viewer having reduced visual acuity, the device comprising: a digital display medium comprising an array of pixels and operable to render a pixelated image accordingly; a microlens array disposed relative to said digital display so to align each said microlens with a corresponding set of said pixels to shape a light field emanating therefrom and thereby at least partially govern a projection thereof from said display medium toward the user; and a hardware processor operable on pixel data for the image to be displayed to output corrected image pixel data to be rendered as a function of a designated characteristic of said microlens array and a selected vision correction parameter related to the viewer’s reduced visual acuity such that said processed image is rendered via said microlens array to at least partially compensate for the user’s reduced visual acuity; wherein a dimension of each said microlens is selected to minimize a spot size on the retina of the viewer produced by given pixels of said corresponding set of pixels.

In accordance with another aspect, there is provided a digital display device to render an input image for viewing by a viewer having reduced visual acuity, the device comprising: a digital display medium comprising an array of pixels and operable to render a pixelated image accordingly; a microlens array disposed relative to said digital display so to dispose each of said microlens over an underlying set of said pixels to shape a light field emanating therefrom and thereby at least partially govern a projection thereof from said display medium toward the viewer; and a hardware processor operable on pixel data for the input image to output adjusted image pixel data to be rendered via said digital display medium and projected through said microlens array in accordance with a stored alignment thereof so to produce a designated image perception adjustment to at least partially address the viewer’s reduced visual acuity; wherein a dimension of each said microlens is selected to minimize a spot size on a retina of the viewer produced by said underlying set of pixels.

In one embodiment, the hardware processor is operable to: digitally map the input image on an adjusted image plane designated to provide the user with said designated image perception adjustment; associate said adjusted image pixel data with at least some of said pixel sets according to said mapping; and render said adjusted image pixel data via said pixel sets thereby rendering a perceptively adjusted version of the input image when viewed through said LFSL.

In one embodiment, the adjusted image plane is a virtual image plane virtually positioned relative to said digital display medium at a designated minimum viewing distance designated such that said perceptively adjusted version of the input image is adjusted to accommodate the viewer’s reduced visual acuity.

In one embodiment, the adjusted image plane is designated as a user retinal plane, wherein said mapping is implemented by scaling the input image on said retinal plane as a function of an input user eye focus aberration parameter.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 3 to about 15 of said pixels.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 3 to about 10 of said pixels.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 5 to about 10 of said pixels.

In one embodiment, the dimension of each said microlens is selected to minimize said spot size on the retina of the viewer produced by each of a set of constituent subpixels for each said corresponding set of pixels.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 3 to about 10 of said pixels.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 5 to about 10 of said pixels.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 10 to about 35 of said pixels.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 15 to 25 of said pixels.

In one embodiment, the microlens array is disposed at a designated distance from said digital display that is shorter than a focal length of said microlens so to produce a divergent light field therefrom.

In one embodiment, the designated distance is selected such that said microlens focuses on a virtual image plane generated thereby.

In accordance with another aspect, there is provided a microlens array for use with a display medium comprising an array of pixels and operable to render a pixelated image accordingly to be viewed by a viewer having a reduced visual acuity, wherein the microlens array is dimensioned to be disposed relative to the digital display medium and comprises an array of microlenses, each one of which being disposed, when overlaid onto the digital display medium, to be centered over a corresponding set of the pixels to shape a light field emanating therefrom and thereby at least partially govern a projection thereof from said display medium toward the user, wherein a dimension of each said microlens is selected to minimize a spot size on the retina of the viewer produced by given pixels of said corresponding set of pixels.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 3 to about 15 of said pixels.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 3 to about 10 of said pixels.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 5 to about 10 of said pixels.

In one embodiment, the dimension of each said microlens is selected to minimize said spot size on the retina of the viewer produced by each of a set of constituent subpixels for each said corresponding set of pixels.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 3 to about 10 of said pixels.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 5 to about 10 of said pixels.

In one embodiment, a diameter of each said microlens is selected to correspond with a dimension of about 10 to about 35 of said pixels.

In one embodiment, the diameter of each said microlens is selected to correspond with a dimension of about 15 to 25 of said pixels.

Other aspects, features and/or advantages will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

Several embodiments of the present disclosure will be provided, by way of examples only, with reference to the appended drawings, wherein:

FIG. 1 is a diagrammatical view of an electronic device having a digital display, in accordance with one embodiment;

FIGS. 2A and 2B are exploded and side views, respectively, of an assembly of a light field display for an electronic device, in accordance with one embodiment;

FIGS. 3A, 3B and 3C schematically illustrate normal vision, blurred vision, and corrected vision in accordance with one embodiment, respectively;

FIG. 4 is a schematic diagram of a single light field pixel defined by a convex lenslet or microlens overlaying an underlying pixel array and disposed at or near its focus to produce a substantially collimated beam, in accordance with one embodiment;

FIG. 5 is another schematic exploded view of an assembly of a light field display in which respective pixel subsets are aligned to emit light through a corresponding microlens or lenslet, in accordance with one embodiment;

FIG. 6 is an exemplary diagram of a light field pattern that, when properly projected by a light field display, produces a corrected image exhibiting reduced blurring for a viewer having reduced visual acuity, in accordance with one embodiment;

FIGS. 7A and 7B are photographs of a Snellen chart, as illustratively viewed by a viewer with reduced acuity without image correction (blurry image in FIG. 7A) and with image correction via a light field display (corrected image in FIG. 7B), in accordance with one embodiment;

FIG. 8 is a schematic diagram of a portion of hexagonal lenslet array disposed at an angle relative to an underlying pixel array and having an irregular pitch mismatch offset, in accordance with one embodiment;

FIGS. 9A and 9B are photographs as illustratively viewed by a viewer with reduced visual acuity without image correction (blurry image in FIG. 9A) and with image correction via a light field display having an angularly mismatched lenslet array (corrected image in FIG. 9B), in accordance with one embodiment;

FIGS. 10A and 10B are photographs as illustratively viewed by a viewer with reduced visual acuity without image correction (blurry image in FIG. 10A) and with image correction via a light field display having an angularly mismatched lenslet array (corrected image in FIG. 10B), in accordance with one embodiment;

FIG. 11 is a process flow diagram of an illustrative ray-tracing rendering process, in accordance with one embodiment;

FIGS. 12 and 13 are process flow diagrams of exemplary input constant parameters and variables, respectively, for the ray-tracing rendering process of FIG. 11 , in accordance with one embodiment;

FIGS. 14A to 14C are schematic diagrams illustrating certain process steps of FIG. 11 ;

FIG. 15 is a process flow diagram of an exemplary process for computing the center position of an associated light field shaping unit in the ray-tracing rendering process of FIG. 11 , in accordance with one embodiment;

FIGS. 16A and 16B are schematic diagrams illustrating an exemplary hexagonal light field shaping layer with a corresponding hexagonal tile array, in accordance with one embodiment;

FIGS. 17A and 17B are schematic diagrams illustrating overlaying a staggered rectangular tile array over the hexagonal tile array of FIGS. 16A and 16B, in accordance with one embodiment;

FIGS. 18A to 18C are schematic diagrams illustrating the associated regions of neighboring hexagonal tiles within a single rectangular tile, in accordance with one embodiment;

FIG. 19 is process flow diagram of an illustrative ray-tracing rendering process, in accordance with another embodiment;

FIGS. 20A to 20D are schematic diagrams illustrating certain process steps of FIG. 19 ;

FIGS. 21A and 21B are schematic diagrams illustrating subpixel rendering, in accordance with one embodiment;

FIGS. 22A and 22B are schematic diagrams of an LCD pixel array defined by respective red (R), green (G) and blue (B) subpixels, and rendering an angular image edge using standard pixel and subpixel rendering, respectively, in accordance with one embodiment;

FIG. 23 is a schematic diagram of one of the pixels of FIG. 22A, showing measures for independently accounting for subpixels thereof to apply subpixel rendering to the display of a corrected image through a light field display, in accordance with one embodiment;

FIGS. 24A to 24E are graphical plots illustrating a variation of a spot size on a user’s retina as a function of a microlens pitch for set operating criteria, in accordance with different embodiments;

FIGS. 25A to 25E are graphical plots illustrating a variation of a spot size on a user’s retina as a function of a microlens pitch for a set of exemplary operating criteria, in accordance with different embodiments;

FIGS. 26A to 26C are schematic diagrams of a substantially collimated, substantially converging or substantially diverging beams, respectively, produced from a convex lenslet or microlens overlaying an underlying pixel array and the associated change in spot size on a user’s retina;

FIG. 27 is a graphical plot illustrating the effect of beam divergence on the variation of a spot size on a user’s retina as a function of a microlens pitch for set operating criteria, in accordance with different embodiments;

FIG. 28 is an illustration of a set of vertical and horizontal black and white striped patterns used to evaluate the vertical and horizontal smallest resolvable point size of a light field display, in accordance with different embodiments; and

FIGS. 29A to 29C are graphical plots illustrating a variation of the vertical and horizontal smallest resolvable point size (in mm) of a light field display as a function user-display distance (in cm), virtual image distance (in diopters), and viewing angle (in degrees), respectively, in accordance with different embodiments.

DETAILED DESCRIPTION

The systems and methods described herein provide, in accordance with different embodiments, different examples of a vision correction system and method, light field display and optical element array therefor, such as, for example, a microlens array. For instance, the devices, displays and methods described herein may allow a user’s perception of an input image to be displayed, to be adjusted or altered using the light field display. For instance, in some examples, users who would otherwise require corrective eyewear such as glasses or contact lenses, or again bifocals, may consume images produced by such devices, displays and methods in clear or improved focus without the use of such eyewear. Other light field display applications, such as 3D displays and the like, may also benefit from the solutions described herein, and thus, should be considered to fall within the general scope and nature of the present disclosure.

For example, some of the herein-described embodiments described herein provide for digital display devices, or devices encompassing such displays, for use by users having reduced visual acuity, whereby images ultimately rendered by such devices can be dynamically processed to accommodate the user’s reduced visual acuity so that they may consume rendered images without the use of corrective eyewear, as would otherwise be required. As noted above, embodiments are not to be limited as such as the notions and solutions described herein may also be applied to other technologies in which a user’s perception of an input image to be displayed can be altered or adjusted via the light field display.

Generally, digital displays as considered herein will comprise a set of image rendering pixels and a light field shaping layer disposed at a preset distance therefrom so to controllably shape or influence a light field emanating therefrom. For instance, each light field shaping layer (i.e. microlens array) will be defined by an array of optical elements centered over a corresponding subset of the display’s pixel array to optically influence a light field emanating therefrom and thereby govern a projection thereof from the display medium toward the user, for instance, providing some control over how each pixel or pixel group will be viewed by the viewer’s eye(s). As will be further detailed below, arrayed optical elements may include, but are not limited to, lenslets, microlenses or other such diffractive optical elements that together form, for example, a lenslet array; pinholes or like apertures or windows that together form, for example, a parallax or like barrier; concentrically patterned barriers, e.g. cut outs and/or windows, such as a to define a Fresnel zone plate or optical sieve, for example, and that together form a diffractive optical barrier (as described, for example, in Applicant’s co-pending U.S. Application Serial No. 15/910,908, the entire contents of which are hereby incorporated herein by reference; and/or a combination thereof, such as for example, a lenslet array whose respective lenses or lenslets are partially shadowed or barriered around a periphery thereof so to combine the refractive properties of the lenslet with some of the advantages provided by a pinhole barrier.

In operation, the display device will also generally invoke a hardware processor operable on image pixel data for an image to be displayed to output corrected image pixel data to be rendered as a function of a stored characteristic of the light field shaping layer (e.g. layer distance from display screen, distance between optical elements (pitch), absolute relative location of each pixel or subpixel to a corresponding optical element, properties of the optical elements (size, diffractive and/or refractive properties, etc.), or other such properties, and a selected vision correction or adjustment parameter related to the user’s reduced visual acuity or intended viewing experience. While light field display characteristics will generally remain static for a given implementation (i.e. a given shaping layer will be used and set for each device irrespective of the user), image processing can, in some embodiments, be dynamically adjusted as a function of the user’s visual acuity or intended application so to actively adjust a distance of the virtual image plane induced upon rendering the corrected/adjusted image pixel data via the static optical layer, for example, or otherwise actively adjust image processing parameters as may be considered, for example, when implementing a viewer-adaptive pre-filtering algorithm or like approach (e.g. compressive light field optimization), so to at least in part govern an image perceived by the user’s eye(s) given pixel-specific light visible thereby through the layer.

Accordingly, a given device may be adapted to compensate for different visual acuity levels and thus accommodate different users and/or uses. For instance, a particular device may be configured to implement and/or render an interactive graphical user interface (GUI) that incorporates a dynamic vision correction scaling function that dynamically adjusts one or more designated vision correction parameter(s) in real-time in response to a designated user interaction therewith via the GUI. For example, a dynamic vision correction scaling function may comprise a graphically rendered scaling function controlled by a (continuous or discrete) user slide motion or like operation, whereby the GUI can be configured to capture and translate a user’s given slide motion operation to a corresponding adjustment to the designated vision correction parameter(s) scalable with a degree of the user’s given slide motion operation. These and other examples are described in Applicant’s co-pending U.S. Pat. Application Serial No. 15/246,255, the entire contents of which are hereby incorporated herein by reference.

With reference to FIG. 1 , and in accordance with one embodiment, a digital display device, generally referred to using the numeral 100, will now be described. In this example, the device 100 is generally depicted as a smartphone or the like, though other devices encompassing a graphical display may equally be considered, such as tablets, e-readers, watches, televisions, GPS devices, laptops, desktop computer monitors, televisions, smart televisions, handheld video game consoles and controllers, vehicular dashboard and/or entertainment displays, and the like.

In the illustrated embodiment, the device 100 comprises a processing unit 110, a digital display 120, and internal memory 130. Display 120 can be an LCD screen, a monitor, a plasma display panel, an LED or OLED screen, or any other type of digital display defined by a set of pixels for rendering a pixelated image or other like media or information. Internal memory 130 can be any form of electronic storage, including a disk drive, optical drive, read-only memory, random-access memory, or flash memory, to name a few examples. For illustrative purposes, memory 130 has stored in it vision correction application 140, though various methods and techniques may be implemented to provide computer-readable code and instructions for execution by the processing unit in order to process pixel data for an image to be rendered in producing corrected pixel data amenable to producing a corrected image accommodating the user’s reduced visual acuity (e.g. stored and executable image correction application, tool, utility or engine, etc.). Other components of the electronic device 100 may optionally include, but are not limited to, one or more rear and/or front-facing camera(s) 150, an accelerometer 160 and/or other device positioning/orientation devices capable of determining the tilt and/or orientation of electronic device 100, and the like.

For example, the electronic device 100, or related environment (e.g. within the context of a desktop workstation, vehicular console/dashboard, gaming or e-learning station, multimedia display room, etc.) may include further hardware, firmware and/or software components and/or modules to deliver complementary and/or cooperative features, functions and/or services. For example, in some embodiment, and as will be described in greater detail below, a pupil/eye tracking system may be integrally or cooperatively implemented to improve or enhance corrective image rending by tracking a location of the user’s eye(s)/pupil(s) (e.g. both or one, e.g. dominant, eye(s)) and adjusting light field corrections accordingly. For instance, the device 100 may include, integrated therein or interfacing therewith, one or more eye/pupil tracking light sources, such as one or more infrared (IR) or near-IR (NIR) light source(s) to accommodate operation in limited ambient light conditions, leverage retinal retro-reflections, invoke corneal reflection, and/or other such considerations. For instance, different IR/NIR pupil tracking techniques may employ one or more (e.g. arrayed) directed or broad illumination light sources to stimulate retinal retro-reflection and/or corneal reflection in identifying a tracking a pupil location. Other techniques may employ ambient or IR/NIR light-based machine vision and facial recognition techniques to otherwise locate and track the user’s eye(s)/pupil(s). To do so, one or more corresponding (e.g. visible, IR/NIR) cameras may be deployed to capture eye/pupil tracking signals that can be processed, using various image/sensor data processing techniques, to map a 3D location of the user’s eye(s)/pupil(s). In the context of a mobile device, such as a mobile phone, such eye/pupil tracking hardware/software may be integral to the device, for instance, operating in concert with integrated components such as one or more front facing camera(s), onboard IR/NIR light source(s) and the like. In other user environments, such as in a vehicular environment, eye/pupil tracking hardware may be further distributed within the environment, such as dash, console, ceiling, windshield, mirror or similarly-mounted camera(s), light sources, etc.

With reference to FIGS. 2A and 2B, the electronic device 100, such as that illustrated in FIG. 1 , is further shown to include a light field shaping layer 200 overlaid atop a display 120 thereof and spaced therefrom via a transparent spacer 310 or other such means as may be readily apparent to the skilled artisan. An optional transparent screen protector is also included atop the layer 200.

For the sake of illustration, the following embodiments will be described within the context of a light field shaping layer defined, at least in part, by a lenslet array comprising an array of microlenses (also interchangeably referred to herein as lenslets) that are each disposed at a distance from a corresponding subset of image rendering pixels in an underlying digital display. It will be appreciated that while a light field shaping layer may be manufactured and disposed as a digital screen overlay, other integrated concepts may also be considered, for example, where light field shaping elements are integrally formed or manufactured within a digital screen’s integral components such as a textured or masked glass plate, beam-shaping light sources or like component. Accordingly, each lenslet will predictively shape light emanating from these pixel subsets to at least partially govern light rays being projected toward the user by the display device. As noted above, other light field shaping layers may also be considered herein without departing from the general scope and nature of the present disclosure, whereby light field shaping will be understood by the person of ordinary skill in the art to reference measures by which light, that would otherwise emanate indiscriminately (i.e. isotropic ally) from each pixel group, is deliberately controlled to define predictable light rays that can be traced between the user and the device’s pixels through the shaping layer.

For greater clarity, a light field is generally defined as a vector function that describes the amount of light flowing in every direction through every point in space. In other words, anything that produces or reflects light has an associated light field. The embodiments described herein produce light fields from an object that are not “natural” vector functions one would expect to observe from that object. This gives it the ability to emulate the “natural” light fields of objects that do not physically exist, such as a virtual display located far behind the light field display, which will be referred to now as the ‘virtual image’. As noted in the examples below, in some embodiments, lightfield rendering may be adjusted to effectively generate a virtual image on a virtual image plane that is set at a designated distance from an input user pupil location, for example, so to effectively push back, or move forward, a perceived image relative to the display device in accommodating a user’s reduced visual acuity (e.g. minimum or maximum viewing distance). In yet other embodiments, lightfield rendering may rather or alternatively seek to map the input image on a retinal plane of the user, taking into account visual aberrations, so to adaptively adjust rendering of the input image on the display device to produce the mapped effect. Namely, where the unadjusted input image would otherwise typically come into focus in front of or behind the retinal plane (and/or be subject to other optical aberrations), this approach allows to map the intended image on the retinal plane and work therefrom to address designated optical aberrations accordingly. Using this approach, the device may further computationally interpret and compute virtual image distances tending toward infinity, for example, for extreme cases of presbyopia. This approach may also more readily allow, as will be appreciated by the below description, for adaptability to other visual aberrations that may not be as readily modeled using a virtual image and image plane implementation. In both of these examples, and like embodiments, the input image is digitally mapped to an adjusted image plane (e.g. virtual image plane or retinal plane) designated to provide the user with a designated image perception adjustment that at least partially addresses designated visual aberrations. Naturally, while visual aberrations may be addressed using these approaches, other visual effects may also be implemented using similar techniques.

In one example, to apply this technology to vision correction, consider first the normal ability of the lens in an eye, as schematically illustrated in FIG. 3A, where, for normal vision, the image is to the right of the eye (C) and is projected through the lens (B) to the retina at the back of the eye (A). As comparatively shown in FIG. 3B, the poor lens shape (F) in presbyopia causes the image to be focused past the retina (D) forming a blurry image on the retina (E). The dotted lines outline the path of a beam of light (G). Naturally, other visual aberrations can and will have different impacts on image formation on the retina. To address these aberrations, a light field display (K), in accordance with some embodiments, projects the correct sharp image (H) to the back of the retina for an eye with a lens which otherwise could not adjust sufficiently to produce a sharp image. The other two light field pixels (I) and (J) are drawn lightly, but would otherwise fill out the rest of the image.

As will be appreciated by the skilled artisan, a light field as seen in FIG. 3C cannot be produced with a ‘normal’ two-dimensional display because the pixels’ light field emits light isotropically. Instead it is necessary to exercise tight control on the angle and origin of the light emitted, for example, using a microlens array or other light field shaping layer such as a parallax barrier, or combination thereof.

Following with the example of a microlens array, FIG. 4 schematically illustrates a single light field pixel defined by a convex microlens (B) disposed at its focus from a corresponding subset pixels in an LCD display (C) to produce a substantially collimated beam of light emitted by these pixels, whereby the direction of the beam is controlled by the location of the pixel(s) relative to the microlens. The single light field pixel produces a beam similar to that shown in FIG. 3C where the outside rays are lighter and the majority inside rays are darker. The LCD display (C) emits light which hits the microlens (B) and it results in a beam of substantially collimated light (A).

Accordingly, upon predictably aligning a particular microlens array with a pixel array, a designated “circle” of pixels will correspond with each microlens and be responsible for delivering light to the pupil through that lens. FIG. 5 schematically illustrates an example of a light field display assembly in which a microlens array (A) sits above an LCD display on a cellphone (C) to have pixels (B) emit light through the microlens array. A ray-tracing algorithm can thus be used to produce a pattern to be displayed on the pixel array below the microlens in order to create the desired virtual image that will effectively correct for the viewer’s reduced visual acuity. FIG. 6 provides an example of such a patter for the letter “Z”.

As will be detailed further below, the separation between the microlens array and the pixel array as well as the pitch of the lenses can be selected as a function of various operating characteristics, such as the normal or average operating distance of the display, and/or normal or average operating ambient light levels.

Further, as producing a light field with angular resolution sufficient for accommodation correction over the full viewing ‘zone’ of a display would generally require an astronomical pixel density, instead, a correct light field can be produced, in some embodiments, only at the location of the user’s pupils. To do so, the light field display can be paired with pupil tracking technology to track a location of the user’s eyes/pupils relative to the display. The display can then compensate for the user’s eye location and produce the correct virtual image, for example, in real time.

In some embodiments, the light field display can render dynamic images at over 30 frames per second on the hardware in a smartphone.

In some embodiments, the light field display can display a virtual image at optical infinity, meaning that any level of accommodation-based presbyopia (e.g. first order) can be corrected for.

In some further embodiments, the light field display can both push the image back and forward, thus allowing for selective image corrections for both hyperopia (farsightedness) and myopia (nearsightedness).

In order to demonstrate a working light field solution, and in accordance with one embodiment, the following test was set up. A camera was equipped with a simple lens, to simulate the lens in a human eye and the aperture was set to simulate a normal pupil diameter. The lens was focused to 50 cm away and a phone was mounted 25 cm away. This would approximate a user whose minimal seeing distance is 50 cm and is attempting to use a phone at 25 cm.

With reading glasses, +2.0 diopters would be necessary for the vision correction. A scaled Snellen chart was displayed on the cellphone and a picture was taken, as shown in FIG. 7A. Using the same cellphone, but with a light field assembly in front that uses that cellphone’s pixel array, a virtual image compensating for the lens focus is displayed. A picture was again taken, as shown in FIG. 7B, showing a clear improvement.

FIGS. 9A and 9B provide another example or results achieved using an exemplary embodiment, in which a colour image was displayed on the LCD display of a Sony™ Xperia™ XZ Premium phone (reported screen resolution of 3840×2160 pixels with 16:9 ratio and approximately 807 pixel-per-inch (ppi) density) without image correction (FIG. 9A) and with image correction through a square fused silica microlens array set at a 2 degree angle relative to the screen’s square pixel array and defined by microlenses having a 7.0 mm focus and 200 µm pitch. In this example, the camera lens was again focused at 50 cm with the phone positioned 30 cm away. Another microlens array was used to produce similar results, and consisted of microlenses having a 10.0 mm focus and 150 µm pitch.

FIGS. 10A and 10B provide yet another example or results achieved using an exemplary embodiment, in which a colour image was displayed on the LCD display of a the Sony™ Xperia™ XZ Premium phone without image correction (FIG. 10A) and with image correction through a square fused silica microlens array set at a 2 degree angle relative to the screen’s square pixel array and defined by microlenses having a 10.0 mm focus and 150 µm pitch. In this example, the camera lens was focused at 66 cm with the phone positioned 40 cm away.

Accordingly, a display device as described above and further exemplified below, can be configured to render a corrected image via the light field shaping layer that accommodates for the user’s visual acuity. By adjusting the image correction in accordance with the user’s actual predefined, set or selected visual acuity level, different users and visual acuity may be accommodated using a same device configuration. That is, in one example, by adjusting corrective image pixel data to dynamically adjust a virtual image distance below/above the display as rendered via the light field shaping layer, different visual acuity levels may be accommodated.

As will be appreciated by the skilled artisan, different image processing techniques may be considered, such as those introduced above and taught by Pamplona and/or Huang, for example, which may also influence other light field parameters to achieve appropriate image correction, virtual image resolution, brightness and the like.

With reference to FIG. 8 , and in accordance with one embodiment, an microlens array configuration will now be described, in accordance with another embodiment, to provide light field shaping elements in a corrective light field implementation. In this embodiment, the microlens array 800 is defined by a hexagonal array of microlenses 802 disposed so to overlay a corresponding square pixel array 804. In doing so, while each microlens 802 can be aligned with a designated subset of pixels to produce light field pixels as described above, the hexagonal-to-square array mismatch can alleviate certain periodic optical artifacts that may otherwise be manifested given the periodic nature of the optical elements and principles being relied upon to produce the desired optical image corrections. Conversely, a square microlens array may be favoured when operating a digital display comprising a hexagonal pixel array.

In some embodiments, as illustrated in FIG. 8 , the microlens array 800 may further or alternatively overlaid at an angle 806 relative to the underlying pixel array, which can further or alternatively alleviate period optical artifacts.

In yet some further or alternative embodiments, a pitch ratio between the microlens array and pixel array may be deliberately selected to further or alternatively alleviate periodic optical artifacts. For example, a perfectly matched pitch ratio (i.e. an exact integer number of display pixels per microlens) is most likely to induce periodic optical artifacts, whereas a pitch ratio mismatch can help reduce such occurrences. Accordingly, in some embodiments, the pitch ratio will be selected to define an irrational number, or at least, an irregular ratio, so to minimize periodic optical artifacts. For instance, a structural periodicity can be defined so to reduce the number of periodic occurrences within the dimensions of the display screen at hand, e.g. ideally selected so to define a structural period that is greater than the size of the display screen being used.

While the following example is provided within the context of a microlens array, similar structural design considerations may be applied within the context of a parallax barrier, diffractive barrier or combination thereof.

With reference to FIGS. 24A to 24E, different plots are shown illustrating the impact certain parameters may have on the performance of a light field display. In these particular examples, the spot size on a user’s retina created by a given pixel (in microns), which generally dictates how many pixels can be projected onto the user’s retina at one time, is plotted as a function of a microlens pitch (or diameter), as measured in pixels (i.e. the number of pixels associated with each microlens). Generally, the ideal solution will be one that minimizes the spot size on the retina for given operating characteristics.

In the calculated examples, illustrated in accordance with certain exemplary embodiments, the ratio of the pupil width (taken as 1 to 3, or preferably 1.5 to 2 times an average pupil diameter to allow for some level of motion without imposing too high a threshold for pupil tracking accuracy capabilities) to the viewing/reading distance was taken be more or less equal to the ratio of the microlens pitch (diameter) to the microlens focal length, the later more or less dictating the distance of the microlens to the pixel array output surface for optimal operation. Furthermore, the viewing/reading distance may also be constrained by the type of application. For example, for a mobile phone display, the viewing distance may be between 30 to 40 cm, while for a digital display located within a vehicle (i.e. vehicular dashboard), the user may be constrained to be positioned at a distance of at least 65 cm or similar.

Furthermore, by matching the two ratios as described above, the pitch ratio (number of pixels per microlens) may then be found to be equal to: (pupil-diameter/viewing-distance)*(focal-distance/pixel-size). In some embodiments, this equation was found to give increased image quality for values of 8 or more. Similarly, in some embodiments, the effect of the periodic optical artifacts mentioned above were found to be minimized, in some embodiments, with the hexagonal microlens array/square pixel array arrangement and a pitch ratio of 8 pixels per microlens or more.

To further refine computed results, in some embodiments, a subpixel coverage factor was considered, namely defining a percentage of the pixel area that is in fact represented by a subpixel light source, thus refining results to actual sub pixel spot size coverage on the user’s retina. For instance, illustrated results were computed for a typical 4K phone display in which a subpixel coverage was set at 100% (FIG. 24A), 35% (FIG. 24B) and 15% (FIG. 24C). Similar results were also computed for an 8K and 16K display (FIGS. 24D and 24E, respectively), in each of which a subpixel coverage was set at 15%.

In each example, an average device viewing distance was set at 40 cm, with a minimum user focal distance set at 6 meters (to define a maximum image correction range, i.e. the furthest a virtual image can be pushed back to accommodate reduced visual acuity in one example), as well as assuming an average eye depth of 25 mm and pupil width of 5 mm.

In some embodiments, an active percentage or fraction of each lens, i.e. a relative transparent area centered on each lens and otherwise circumscribed by a darkened or masked periphery, such as to combine the benefits of microlens beam shaping with parallax barrier effects, can also be considered to further refine optimizations.

Using any of these calculations, an appropriate microlens array may be selected, for example, based on an intended application (viewer distance), display screen technology (pixel size, subpixel coverage, pixel resolution), visual aberration correction, etc. For example, using the results of FIG. 24B for a 4K screen having 35% subpixel coverage, microlenses having a diameter corresponding to anywhere between about 5 and 10 pixels should produce optimal results (as compared to 10-15 pixels for 100% subpixel coverage and 3-7 pixels for 15% subpixel coverage on a similarly defined 4K screen; 3-10 pixels on an 8K screen; and 5-15 for a 16K screen). As smaller microlens diameters result in being able to optimally bring the microlens array closer to the display screen, these calculations may be used to seek out a smallest diameter possible without unduly limiting optimal retinal spot size formation. The optimized microlens diameter can also be used to select the microlens focus length as prescribed by the above-note ratios.

While the above-described embodiments are sufficient for providing high quality light-field corrected images. In some embodiments, it may be advantageous to further include additional parameters, such as the width of the light beam emerging from a microlens at the corneal surface and the width of the unlit edge of the beam as it focuses behind the retina.

With reference to FIGS. 25A to 25E, and in accordance with another exemplary embodiment, different plots are shown illustrating the impact certain parameters may have on the performance of a light field display. The spot size on a user’s retina created by a given pixel (in microns) is again plotted as a function of a microlens pitch (or diameter), as measured in pixels. However, in this exemplary embodiment, the effect of both the width of the light beam emerging from a microlens at the corneal surface and the width of the unlit edge of the beam as it focuses behind the retina were incorporated. The illustrated results were again computed for a typical 4K phone display in which subpixel coverage was set at 100% (FIG. 25A), 35% (FIG. 25B) and 15% (FIG. 25C). Similar results were also computed for an 8K and 16K display (FIGS. 10D and 10E, respectively), in each of which a subpixel coverage was set at 15%. However, herein the viewing distance was set to 65 cm and the pupil width to 4 mm (i.e. for vehicular applications). The ideal microlens pitch is once more taken as one that minimizes the spot size on the retina for given operating characteristics.

Using any of these calculations, according to this embodiment, an appropriate microlens array may be selected, for example, based on an intended application (viewer distance), display screen technology (pixel size, subpixel coverage, pixel resolution), visual aberration correction, etc. For example, using the results of FIG. 10B for a 4K screen having 35% subpixel coverage, microlenses having a diameter corresponding to anywhere between about 17 to 22 pixels should produce optimal results (as compared to 30-35 pixels for 100% subpixel coverage and 10-12 pixels for 15% subpixel coverage on a similarly defined 4K screen; 15-20 pixels on an 8K screen; and 20-30 for a 16K screen).

Accordingly, the methods and approaches described herein allow for the non-trivial determination of optimal optical hardware characteristics that can be applied to a particular display device, user application, and/or other such characteristics.

The skilled artisan will understand, based on the parameters disclosed above, that different combinations of microlens array/digital display may be available, depending on the application and applied minimum spot size. The table below lists an exemplary set of digital displays that have been used to demonstrate a working light field solution:

TABLE 1 DISPLAY # Resolution (x/y pixels) Pixel size (microns) Subpixel coverage (x %,y %) 1 3840×2160 31.5 (38, 67) 2 3840×2160 72.0 (27, 70) 3 1920×1080 8.1 (50, 50) 4 2048×1080 47.25 (23, 60) The table includes the display’s resolution, the pixel size in microns and the subpixel coverage (in % both the x and y directions). Notably, display #1 is taken from the Sony™ Xperia™ XZ Premium phone while the other displays are attainable from manufacturers or readily modified from other devices.

Similarly, the table below lists some exemplary microlens array designs operable to be used with some or all the displays disclosed in the table above:

TABLE 2 MLA # Manufacturer Focal length (mm) Pitch (mm) Viewing distance (cm) Geometry 1 Fraunhofer 43.0 0.521 65 hexagonal 2 Fraunhofer 65.0 1.000 65 hexagonal 3 Fraunhofer 43.0 0.600 65 hexagonal 4 Edmund Optics 15.3 0.500 30 square 5 RPC 3.5 0.125 30 square 6 Okotech 10.0 0.150 30 square 7 Okotech 7.0 0.200 30 square

For each microlens array listed, indicated are the focal length (mm), the pitch of each individual microlenses (in mm), the expected optimal viewing distance (in cm) and its geometry (hexagonal or square). While using any combination of microlens array/display are operable to provide a functional light field, some combinations may provide higher perceived resolutions (smaller spot size on the user’s retina), based on the parameters discussed above. For example, the Fraunhofer microlens arrays (#1, #2 and #3) were specifically designed to be used with display #1, based on the above-described optimization of the functional parameters affecting the spot size on the user’s retina. In contrast, the Edmund Optics microlens array (#4) is a small microlens (10 mm x 10 mm) used for preliminary testing with a focal length best suited for a 30 cm viewing distance with the Z5 screen (display #1) while the RPC microlens array (#5) was used for a close-to-eye test, generally only a few centimeters from the eye. Finally, the Okotech 10 mm (#6) and 7 mm (#7) are off the shelf MLAs. Examples of such combinations of digital displays/microlens arrays from the above tables will be discussed below.

In order to demonstrate a working light field solution, and in accordance with one embodiment, the following test was set up. A camera was equipped with a simple lens, to simulate the lens in a human eye and the aperture was set to simulate a normal pupil diameter. These factors are generally controlled to adequately simulate the depth of focus of the human eye. The lens was focused to 50 cm away and a phone was mounted 25 cm away. This would approximate a user whose minimal seeing distance is 50 cm and is attempting to use a phone at 25 cm.

With reading glasses, +2.0 diopters would be necessary for the vision correction. A scaled Snellen chart was displayed on the cellphone and a picture was taken, as shown in FIG. 7A. Using the same cellphone, but with a light field assembly in front that uses that cellphone’s pixel array, a virtual image compensating for the lens focus is displayed. A picture was again taken, as shown in FIG. 7B, showing a clear improvement.

FIGS. 9A and 9B provide another example or results achieved using an exemplary embodiment, in which a color image was displayed on the LCD display #1 (a Sony™ Xperia™ XZ Premium phone with a reported screen resolution of 3840x2160 pixels with 16:9 ratio and approximately 807 pixel-per-inch (ppi) density) without image correction (FIG. 9A) and with image correction through a square fused silica microlens array set at a 2 degree angle relative to the screen’s square pixel array and defined by microlenses #7 having a 7.0 mm focus and 200 µm pitch. In this example, the camera lens was again focused at 50 cm with the phone positioned 30 cm away. Another microlens array was used to produce similar results, and consisted of microlens array #6 having microlenses with a 10.0 mm focus and 150 µm pitch.

FIGS. 10A and 10B provide yet another example or results achieved using an exemplary embodiment, in which a color image was displayed on the LCD display of a Sony™ Xperia™ XZ Premium phone (display #1) without image correction (FIG. 10A) and with image correction through a square fused silica microlens array set at a 2 degree angle relative to the screen’s square pixel array and defined by microlens array #6 having microlenses with a 10.0 mm focus and 150 µm pitch. In this example, the camera lens was focused at 66 cm with the phone positioned 40 cm away.

While the two above examples were provided using off-the-shelf components, the Fraunhofer microlens arrays (#1, #2 and #3) described above were specifically designed, using the spot size minimization procedure described above, to be combined with display #1 (Sony™ Xperia™ XZ Premium phone) and were found to provide an improved resolution that substantially approaches the so-called retina resolution.

In some embodiments, the microlens array and the digital display may be relatively positioned so that each microlens produces moderately convergent or divergent light beams. By adjusting the beam convergence/divergence by changing the relative position of the microlens and the display with respect to the microlens’ focal length, the width of the spot size on the user’s retina may be minimized as well. FIGS. 26A to 26C schematically illustrates the effect using a different microlens focus has on the width of the spot size on the retina. Indeed, for a microlens with a pixel located on its focal plane, the emerging beam is collimated (parallel) and thus the width of the beam on the cornea is the width of the microlens. In contrast, if the focal plane is located instead in front/behind the pixel (e.g. pixel is further/closer than focal length), then the emerging beam converges/diverges and the width of the beam on the cornea will be smaller/greater than the width (or pitch) of the microlens. In FIG. 26A, three collimated beams exiting microlens plane 2605 are shown, each associated with a single pixel from the display (not shown) as described above with respect to FIG. 4 . The rays from each beam are directed towards the cornea/crystallin plane 2608 and converge on focal plane 2615, which is located behind the retina plane 2618. The perceived spot size 2625 is the width of the region covered by the beams on the retina plane 2618. The associated virtual image portion covered by each beam, as perceived by the user, on the virtual image plane 2631 behind microlens 2605 is also shown for comparison. Similarly, FIGS. 26B and 26C illustrates the perceived spot sizes 2637 and 2645, respectively, for the same configuration but with the microlens focused at the cornea (e.g. converging beam) or focused at the virtual image plane (e.g. diverging beam), respectively. For the diverging beam (FIG. 26C), the resulting spot size 2645 is smaller than the spot sizes 2625 or 2637 for the collimated beam and the converging beam, respectively. This effect of beam divergence of the spot size is further illustrated in FIG. 27 . Starting with the same calculations used to generate FIG. 25C, a beam divergence parameter was further added to measure the effect of increased beam divergence on the spot size on a user’s retina created by a given pixel (in microns), herein again plotted as a function of a microlens pitch (or diameter), as measured in pixels. For comparison, plot 2705 is the same plot as the one shown in FIG. 25C (e.g. perfectly collimated beam) while plot 2713 is a plot obtained using the same parameters but with an added increased beam divergence. The divergence of the beam emerging from the microlens may be quantified using, for example, the inverse distance from the microlens to the convergence point of the beam emanating from it. For a divergent beam (e.g. that converges “behind” the lens), this inverse distance parameter will be negative. Plot 2713 was obtained with a divergence parameter equal to the negative inverse distance to the virtual image plane, representing a microlens focused on the virtual image plane (same as seen in FIG. 26C). We clearly see the resulting improvement on the minimum perceived spot size 2717 vs the original optimized value 2709, which shifts from a minimum value of about 3.3 microns to a minimum value of about 1.08 microns.

With reference to FIGS. 11 to 13 , and in accordance with one embodiment, an exemplary computationally implemented ray-tracing method for rendering a corrected image via the light field shaping layer (LFSL) that accommodates for the user’s reduced visual acuity will now be described. In this exemplary embodiment, a set of constant parameters 1102 may be pre-determined. These may include, for example, any data that are not expected to significantly change during a user’s viewing session, for instance, which are generally based on the physical and functional characteristics of the display for which the method is to be implemented, as will be explained below. Similarly, every iteration of the rendering algorithm may use a set of input variables 1104 which are expected to change either at each rendering iteration or at least between each user’s viewing session.

As illustrated in FIG. 12 , the list of constant parameters 1102 may include, without limitations, the distance 1204 between the display and the LFSL, the in-plane rotation angle 1206 between the display and LFSL frames of reference, the display resolution 1208, the size of each individual pixel 1210, the optical LFSL geometry 1212, the size of each optical element 1214 within the LFSL and optionally the subpixel layout 1216 of the display. Moreover, both the display resolution 1208 and the size of each individual pixel 1210 may be used to pre-determine both the absolute size of the display in real units (i.e. in mm) and the three-dimensional position of each pixel within the display. In some embodiments where the subpixel layout 1216 is available, the position within the display of each subpixel may also be pre-determined. These three-dimensional location/positions are usually calculated using a given frame of reference located somewhere within the plane of the display, for example a corner or the middle of the display, although other reference points may be chosen. Concerning the optical layer geometry 1212, different geometries may be considered, for example a hexagonal geometry such as the one shown in FIG. 8 . Finally, by combining the distance 1204, the rotation angle 1206, and the geometry 1212 with the optical element size 1214, it is possible to similarly pre-determine the three-dimensional location/position of each optical element center with respect to the display’s same frame of reference.

FIG. 13 meanwhile illustratively lists an exemplary set of input variables 1104 for method 1100, which may include any input data fed into method 1100 that may reasonably change during a user’s single viewing session, and may thus include without limitation: the image(s) to be displayed 1306 (e.g. pixel data such as on/off, colour, brightness, etc.), the three-dimensional pupil location 1308 (e.g. in embodiments implementing active eye/pupil tracking methods) and/or pupil size 1312 and the minimum reading distance 1310 (e.g. one or more parameters representative of the user’s reduced visual acuity or condition). In some embodiments, the eye depth 1314 may also be used. The image data 1306, for example, may be representative of one or more digital images to be displayed with the digital pixel display. This image may generally be encoded in any data format used to store digital images known in the art. In some embodiments, images 1306 to be displayed may change at a given framerate.

The pupil location 1308, in one embodiment, is the three-dimensional coordinates of at least one the user’s pupils’ center with respect to a given reference frame, for example a point on the device or display. This pupil location 1308 may be derived from any eye/pupil tracking method known in the art. In some embodiments, the pupil location 1308 may be determined prior to any new iteration of the rendering algorithm, or in other cases, at a lower framerate. In some embodiments, only the pupil location of a single user’s eye may be determined, for example the user’s dominant eye (i.e. the one that is primarily relied upon by the user). In some embodiments, this position, and particularly the distance pupil distance to the screen may otherwise or additionally be rather approximated or adjusted based on other contextual or environmental parameters, such as an average or preset user distance to the screen (e.g. typical reading distance for a given user or group of users; stored, set or adjustable driver distance in a vehicular environment; etc.).

In the illustrated embodiment, the minimum reading distance 1310 is defined as the minimal focus distance for reading that the user’s eye(s) may be able to accommodate (i.e. able to view without discomfort). In some embodiments, different values of the minimum reading distance 1310 associated with different users may be entered, for example, as can other adaptive vision correction parameters be considered depending on the application at hand and vision correction being addressed.

With added reference to FIGS. 14A to 14C, once parameters 1102 and variables 1104 have been set, the method of FIG. 11 then proceeds with step 1106, in which the minimum reading distance 1310 (and/or related parameters) is used to compute the position of a virtual (adjusted) image plane 1405 with respect to the device’s display, followed by step 1108 wherein the size of image 1306 is scaled within the image plane 1405 to ensure that it correctly fills the pixel display 1401 when viewed by the distant user. This is illustrated in FIG. 14A, which shows a diagram of the relative positioning of the user’s pupil 1415, the light field shaping layer 1403, the pixel display 1401 and the virtual image plane 1405. In this example, the size of image 1306 in image plane 1405 is increased to avoid having the image as perceived by the user appear smaller than the display’s size.

An exemplary ray-tracing methodology is described in steps 1110 to 1128 of FIG. 11 , at the end of which the output color of each pixel of pixel display 1401 is known so as to virtually reproduce the light field emanating from an image 1306 positioned at the virtual image plane 1405. In FIG. 11 , these steps are illustrated in a loop over each pixel in pixel display 1401, so that each of steps 1110 to 1126 describes the computations done for each individual pixel. However, in some embodiments, these computations need not be executed sequentially, but rather, steps 1110 to 1128 may executed in parallel for each pixel or a subset of pixels at the same time. Indeed, as will be discussed below, this exemplary method is well suited to vectorization and implementation on highly parallel processing architectures such as GPUs.

As illustrated in FIG. 14A, in step 1110, for a given pixel 1409 in pixel display 1401, a trial vector 1413 is first generated from the pixel’s position to the center position 1417 of pupil 1415. This is followed in step 1112 by calculating the intersection point 1411 of vector 1413 with the LFSL 1403.

The method then finds, in step 1114, the coordinates of the center 1416 of the LFSL optical element closest to intersection point 1411. This step may be computationally intensive and will be discussed in more depth below. Once the position of the center 1416 of the optical element is known, in step 1116, a normalized unit ray vector is generated from drawing and normalizing a vector 1423 drawn from center position 1416 to pixel 1409. This unit ray vector generally approximates the direction of the light field emanating from pixel 1409 through this particular light field element, for instance, when considering a parallax barrier aperture or lenslet array (i.e. where the path of light travelling through the center of a given lenslet is not deviated by this lenslet). Further computation may be required when addressing more complex light shaping elements, as will be appreciated by the skilled artisan. The direction of this ray vector will be used to find the portion of image 1306, and thus the associated color, represented by pixel 1409. But first, in step 1118, this ray vector is projected backwards to the plane of pupil 1415, and then in step 1120, the method verifies that the projected ray vector 1425 is still within pupil 1415 (i.e. that the user can still “see” it). Once the intersection position, for example location 1431 in FIG. 14B, of projected ray vector 1425 with the pupil plane is known, the distance between the pupil center 1417 and the intersection point 1431 may be calculated to determine if the deviation is acceptable, for example by using a pre-determined pupil size and verifying how far the projected ray vector is from the pupil center.

If this deviation is deemed to be too large (i.e. light emanating from pixel 1409 channeled through optical element 1416 is not perceived by pupil 1415), then in step 1122, the method flags pixel 1409 as unnecessary and to simply be turned off or render a black color. Otherwise, as shown in FIG. 14C, in step 1124, the ray vector is projected once more towards virtual image plane 1405 to find the position of the intersection point 1423 on image 1306. Then in step 1126, pixel 1409 is flagged as having the color value associated with the portion of image 1306 at intersection point 1423.

In some embodiments, method 1100 is modified so that at step 1120, instead of having a binary choice between the ray vector hitting the pupil or not, one or more smooth interpolation function (i.e. linear interpolation, Hermite interpolation or similar) are used to quantify how far or how close the intersection point 1431 is to the pupil center 1417 by outputting a corresponding continuous value between 1 or 0. For example, the assigned value is equal to 1 substantially close to pupil center 1417 and gradually change to 0 as the intersection point 1431 substantially approaches the pupil edges or beyond. In this case, the branch containing step 1122 is ignored and step 1220 continues to step 1124. At step 1126, the pixel color value assigned to pixel 1409 is chosen to be somewhere between the full color value of the portion of image 1306 at intersection point 1423 or black, depending on the value of the interpolation function used at step 1120 (1 or 0).

In yet other embodiments, pixels found to illuminate a designated area around the pupil may still be rendered, for example, to produce a buffer zone to accommodate small movements in pupil location, for example, or again, to address potential inaccuracies, misalignments or to create a better user experience.

In some embodiments, steps 1118, 1120 and 1122 may be avoided completely, the method instead going directly from step 1116 to step 1124. In such an exemplary embodiment, no check is made that the ray vector hits the pupil or not, but instead the method assumes that it always does.

Once the output colors of all pixels have been determined, these are finally rendered in step 1130 by pixel display 1401 to be viewed by the user, therefore presenting a light field corrected image. In the case of a single static image, the method may stop here. However, new input variables may be entered and the image may be refreshed at any desired frequency, for example because the user’s pupil moves as a function of time and/or because instead of a single image a series of images are displayed at a given framerate.

With reference to FIGS. 19 and 20A to 20D, and in accordance with one embodiment, another exemplary computationally implemented ray-tracing method for rendering an adjusted image via the light field shaping layer (LFSL) that accommodates for the user’s reduced visual acuity, for example, will now be described. In this embodiment, the adjusted image portion associated with a given pixel/subpixel is computed (mapped) on the retina plane instead of the virtual image plane considered in the above example, again in order to provide the user with a designated image perception adjustment. Therefore, the currently discussed exemplary embodiment shares some steps with the method of FIG. 11 . Indeed, a set of constant parameters 1402 may also be pre-determined. These may include, for example, any data that are not expected to significantly change during a user’s viewing session, for instance, which are generally based on the physical and functional characteristics of the display for which the method is to be implemented, as will be explained below. Similarly, every iteration of the rendering algorithm may use a set of input variables 1404 which are expected to change either at each rendering iteration or at least between each user viewing session. The list of possible variables and constants is substantially the same as the one disclosed in FIGS. 12 and 13 and will thus not be replicated here.

Once parameters 1402 and variables 1404 have been set, this second exemplary ray-tracing methodology proceeds from steps 1910 to 1936, at the end of which the output color of each pixel of the pixel display is known so as to virtually reproduce the light field emanating from an image perceived to be positioned at the correct or adjusted image distance, in one example, so to allow the user to properly focus on this adjusted image (i.e. having a focused image projected on the user’s retina) despite a quantified visual aberration. In FIG. 19 , these steps are illustrated in a loop over each pixel in pixel display 1401, so that each of steps 1910 to 1934 describes the computations done for each individual pixel. However, in some embodiments, these computations need not be executed sequentially, but rather, steps 1910 to 1934 may be executed in parallel for each pixel or a subset of pixels at the same time. Indeed, as will be discussed below, this second exemplary method is also well suited to vectorization and implementation on highly parallel processing architectures such as GPUs.

Referencing once more FIG. 14A, in step 1910 (as in step 1110), for a given pixel in pixel display 1401, a trial vector 1413 is first generated from the pixel’s position to pupil center 1417 of the user’s pupil 1415. This is followed in step 1912 by calculating the intersection point of vector 1413 with optical layer 1403.

From there, in step 1914, the coordinates of the optical element center 1416 closest to intersection point 1411 are determined. This step may be computationally intensive and will be discussed in more depth below. As shown in FIG. 14B, once the position of the optical element center 1416 is known, in step 1916, a normalized unit ray vector is generated from drawing and normalizing a vector 1423 drawn from optical element center 1416 to pixel 1409. This unit ray vector generally approximates the direction of the light field emanating from pixel 1409 through this particular light field element, for instance, when considering a parallax barrier aperture or lenslet array (i.e. where the path of light travelling through the center of a given lenslet is not deviated by this lenslet). Further computation may be required when addressing more complex light shaping elements, as will be appreciated by the skilled artisan. In step 1918, this ray vector is projected backwards to pupil 1415, and then in step 1920, the method ensures that the projected ray vector 1425 is still within pupil 1415 (i.e. that the user can still “see” it). Once the intersection position, for example location 1431 in FIG. 14B, of projected ray vector 1425 with the pupil plane is known, the distance between the pupil center 1417 and the intersection point 1431 may be calculated to determine if the deviation is acceptable, for example by using a pre-determined pupil size and verifying how far the projected ray vector is from the pupil center.

Now referring to FIGS. 20A to 20D, steps 1921 to 1929 of method 1900 will be described. Once optical element center 1416 of the relevant optical unit has been determined, at step 1921, a vector 2004 is drawn from optical element center 1416 to pupil center 1417. Then, in step 1923, vector 2004 is projected further behind the pupil plane onto focal plane 2006 (location where any light rays originating from optical layer 1403 would be focused by the eye’s lens) to locate focus point 2008. For a user with perfect vision, focal plane 2006 would be located at the same location as retina plane 2010, but in this example, focal plane 2006 is located behind retina plane 2006, which would be expected for a user with some form of farsightedness. The position of focal plane 2006 may be derived from the user’s minimum reading distance 1310, for example, by deriving therefrom the focal length of the user’s eye. Other manually input or computationally or dynamically adjustable means may also or alternatively considered to quantify this parameter.

The skilled artisan will note that any light ray originating from optical element center 1416, no matter its orientation, will also be focused onto focus point 2008, to a first approximation. Therefore, the location on retina plane (2012) onto which light entering the pupil at intersection point 1431 will converge may be approximated by drawing a straight line between intersection point 1431 where ray vector 1425 hits the pupil 1415 and focus point 2008 on focal plane 2006. The intersection of this line with retina plane 2010 (retina image point 2012) is thus the location on the user’s retina corresponding to the image portion that will be reproduced by corresponding pixel 1409 as perceived by the user. Therefore, by comparing the relative position of retina point 2012 with the overall position of the projected image on the retina plane 2010, the relevant adjusted image portion associated with pixel 1409 may be computed.

To do so, at step 1927, the corresponding projected image center position on retina plane 2010 is calculated. Vector 2016 is generated originating from the center position of display 1401 (display center position 2018) and passing through pupil center 1417. Vector 2016 is projected beyond the pupil plane onto retina plane 2010, wherein the associated intersection point gives the location of the corresponding retina image center 2020 on retina plane 2010. The skilled technician will understand that step 1927 could be performed at any moment prior to step 1929, once the relative pupil center location 1417 is known in input variables step 1904. Once image center 2020 is known, one can then find the corresponding image portion of the selected pixel/subpixel at step 1929 by calculating the x/y coordinates of retina image point 2012 relative to retina image center 2020 on the retina, scaled to the x/y retina image size 2031.

This retina image size 2031 may be computed by calculating the magnification of an individual pixel on retina plane 2010, for example, which may be approximately equal to the x or y dimension of an individual pixel multiplied by the eye depth 1314 and divided by the absolute value of the distance to the eye (i.e. the magnification of pixel image size from the eye lens). Similarly, for comparison purposes, the input image is also scaled by the image x/y dimensions to produce a corresponding scaled input image 2064. Both the scaled input image and scaled retina image should have a width and height between -0.5 to 0.5 units, enabling a direct comparison between a point on the scaled retina image 2010 and the corresponding scaled input image 2064, as shown in FIG. 20D.

From there, the image portion position 2041 relative to retina image center position 2043 in the scaled coordinates (scaled input image 2064) corresponds to the inverse (because the image on the retina is inverted) scaled coordinates of retina image point 2012 with respect to retina image center 2020. The associated color with image portion position 2041 is therefrom extracted and associated with pixel 1409.

In some embodiments, method 1900 may be modified so that at step 1920, instead of having a binary choice between the ray vector hitting the pupil or not, one or more smooth interpolation function (i.e. linear interpolation, Hermite interpolation or similar) are used to quantify how far or how close the intersection point 1431 is to the pupil center 1417 by outputting a corresponding continuous value between 1 or 0. For example, the assigned value is equal to 1 substantially close to pupil center 1417 and gradually change to 0 as the intersection point 1431 substantially approaches the pupil edges or beyond. In this case, the branch containing step 1122 is ignored and step 1920 continues to step 1124. At step 1931, the pixel color value assigned to pixel 1409 is chosen to be somewhere between the full color value of the portion of image 1306 at intersection point 1423 or black, depending on the value of the interpolation function used at step 1920 (1 or 0).

In yet other embodiments, pixels found to illuminate a designated area around the pupil may still be rendered, for example, to produce a buffer zone to accommodate small movements in pupil location, for example, or again, to address potential inaccuracies or misalignments.

Once the output colors of all pixels in the display have been determined (check at step 1934 is true), these are finally rendered in step 1936 by pixel display 1401 to be viewed by the user, therefore presenting a light field corrected image. In the case of a single static image, the method may stop here. However, new input variables may be entered and the image may be refreshed at any desired frequency, for example because the user’s pupil moves as a function of time and/or because instead of a single image a series of images are displayed at a given framerate.

As will be appreciated by the skilled artisan, selection of the adjusted image plane onto which to map the input image in order to adjust a user perception of this input image allows for different ray tracing approaches to solving a similar challenge, that is of creating an adjusted image using the light field display that can provide an adjusted user perception, such as addressing a user’s reduce visual acuity. While mapping the input image to a virtual image plane set at a designated minimum (or maximum) comfortable viewing distance can provide one solution, the alternate solution may allow accommodation of different or possibly more extreme visual aberrations. For example, where a virtual image is ideally pushed to infinity (or effectively so), computation of an infinite distance becomes problematic. However, by designating the adjusted image plane as the retinal plane, the illustrative process of FIG. 19 can accommodate the formation of a virtual image effectively set at infinity without invoking such computational challenges. Likewise, while first order focal length aberrations are illustratively described with reference to FIG. 19 , higher order or other optical anomalies may be considered within the present context, whereby a desired retinal image is mapped out and traced while accounting for the user’s optical aberration(s) so to compute adjusted pixel data to be rendered in producing that image. These and other such considerations should be readily apparent to the skilled artisan.

While the computations involved in the above described ray-tracing algorithms (steps 1110 to 1128 of FIG. 11 or steps 1920 to 1934 of FIG. 19 ) may be done on general CPUs, it may be advantageous to use highly parallel programming schemes to speed up such computations. While in some embodiments, standard parallel programming libraries such as Message Passing Interface (MPI) or OPENMP may be used to accelerate the light field rendering via a general-purpose CPU, the light field computations described above are especially tailored to take advantage of graphical processing units (GPU), which are specifically tailored for massively parallel computations. Indeed, modern GPU chips are characterized by the very large number of processing cores, and an instruction set that is commonly optimized for graphics. In typical use, each core is dedicated to a small neighborhood of pixel values within an image, e.g., to perform processing that applies a visual effect, such as shading, fog, affine transformation, etc. GPUs are usually also optimized to accelerate exchange of image data between such processing cores and associated memory, such as RGB frame buffers. Furthermore, smartphones are increasingly being equipped with powerful GPUs to speed the rendering of complex screen displays, e.g., for gaming, video, and other image-intensive applications. Several programming frameworks and languages tailored for programming on GPUs include, but are not limited to, CUDA, OpenCL, OpenGL Shader Language (GLSL), High-Level Shader Language (HLSL) or similar. However, using GPUs efficiently may be challenging and thus require creative steps to leverage their capabilities, as will be discussed below.

With reference to FIGS. 15 to 18C and in accordance with one exemplary embodiment, an exemplary process for computing the center position of an associated light field shaping element in the ray-tracing process of FIG. 11 (or FIG. 19 ) will now be described. The series of steps are specifically tailored to avoid code branching, so as to be increasingly efficient when run on GPUs (i.e. to avoid so called “warp divergence”). Indeed, with GPUs, because all the processors must execute identical instructions, divergent branching can result in reduced performance.

With reference to FIG. 15 , and in accordance with one embodiment, step 1114 of FIG. 11 is expanded to include steps 1515 to 1525. A similar discussion can readily be made in respect of step 1914 of FIG. 19 , and thus need not be explicitly detailed herein. The method receives from step 1112 the 2D coordinates of the intersection point 1411 (illustrated in FIG. 14A) of the trial vector 1413 with optical layer 1403. As discussed with respect to the exemplary embodiment of FIG. 8 , there may be a difference in orientation between the frames of reference of the optical layer (hexagonal array of microlenses 802 in FIG. 8 , for example) and of the corresponding pixel display (square pixel array 804 in FIG. 8 , for example). This is why, in step 1515, these input intersection coordinates, which are initially calculated from the display’s frame of reference, may first be rotated to be expressed from the light field shaping layer’s frame of reference and optionally normalized so that each individual light shaping element has a width and height of 1 unit. The following description will be equally applicable to any light field shaping layer having an hexagonal geometry like the exemplary embodiment of FIG. 8 . Note however that the method steps 1515 to 1525 described herein may be equally applied to any kind of light field shaping layer sharing the same geometry (i.e. not only a microlens array, but pinhole arrays as well, etc.). Likewise, while the following example is specific to an exemplary hexagonal array of LFSL elements definable by a hexagonal tile array of regular hexagonal tiles, other geometries may also benefit from some or all of the features and/or advantages of the herein-described and illustrated embodiments. For example, different hexagonal LFSL element arrays, such as stretched, skewed and/or rotated arrays may be considered, as can other nestled array geometries in which adjacent rows and/or columns of the LFSL array at least partially “overlap” or inter-nest. For instance, as will be described further below, hexagonal arrays and like nestled array geometries will generally provide for a commensurately sized rectangular/square tile of an overlaid rectangular/square array or grid to naturally encompass distinct regions as defined by two or more adjacent underlying nestled array tiles, which can be used to advantage in the examples provided below. In yet other embodiments, the processes discussed herein may be applied to rectangular and/or square LFSL element arrays. Other LFSL element array geometries may also be considered, as will be appreciated by the skilled artisan upon reading of the following example, without departing from the general scope and nature of the present disclosure.

For hexagonal geometries, as illustrated in FIGS. 16A and 16B, the hexagonal symmetry of the light field shaping layer 1403 may be represented by drawing an array of hexagonal tiles 1601, each centered on their respective light field shaping element, so that the center of a hexagonal tile element is more or less exactly the same as the center position of its associated light field shaping element. Thus, the original problem is translated to a slightly similar one whereby one now needs to find the center position 1615 of the associated hexagonal tile 1609 closest to the intersection point 1411, as shown in FIG. 16B.

To solve this problem, the array of hexagonal tiles 1601 may be superimposed on or by a second array of staggered rectangular tiles 1705, in such a way as to make an “inverted house” diagram within each rectangle, as clearly illustrated in FIG. 17A, namely defining three linearly segregated tile regions for each rectangular tile, one region predominantly associated with a main underlying hexagonal tile, and two other opposed triangular regions associated with adjacent underlying hexagonal tiles. In doing so, the nestled hexagonal tile geometry is translated to a rectangular tile geometry having distinct linearly segregated tile regions defined therein by the edges of underlying adjacently disposed hexagonal tiles. Again, while regular hexagons are used to represent the generally nestled hexagonal LFSL element array geometry, other nestled tile geometries may be used to represent different nestled element geometries. Likewise, while a nestled array is shown in this example, different staggered or aligned geometries may also be used, in some examples, in some respects, with reduced complexity, as further described below.

Furthermore, while this particular example encompasses the definition of linearly defined tile region boundaries, other boundary types may also be considered provided they are amenable to the definition of one or more conditional statements, as illustrated below, that can be used to output a corresponding set of binary or Boolean values that distinctly identify a location of a given point within one or another of these regions, for instance, without invoking, or by limiting, processing demands common to branching or looping decision logics/trees/statements/etc.

Following with hexagonal example, to locate the associated hexagon tile center 1615 closest to the intersection point 1411, in step 1517, the method first computes the 2D position of the bottom left corner 1707 of the associated (normalized) rectangular tile element 1609 containing intersection point 1411, as shown in FIG. 17B, which can be calculated without using any branching statements by the following two equations (here in normalized coordinates wherein each rectangle has a height and width of one unit):

$\overset{\rightarrow}{t} = \left( {floor\left( {uv_{y}} \right),0} \right)$

${\overset{\rightarrow}{C}}_{corner} = \left( {\overset{\rightarrow}{uv} + \overset{\rightarrow}{t}} \right) - \overset{\rightarrow}{t}$

where

$\overset{\rightarrow}{uv}$

is the position vector of intersection point 1411 in the common frame of reference of the hexagonal and staggered rectangular tile arrays, and the floor() function returns the greatest integer less than or equal to each of the xy coordinates of

$\overset{\rightarrow}{uv}.$

Once the position of lower left corner 1707, indicated by vector C _(corner) 1701, of the associated rectangular element 1814 containing the intersection point 1411 is known, three regions 1804, 1806 and 1807 within this rectangular element 1814 may be distinguished, as shown in FIGS. 18A to 18C. Each region is associated with a different hexagonal tile, as shown in FIG. 18A, namely, each region is delineated by the linear boundaries of adjacent underlying hexagonal tiles to define one region predominantly associated with a main hexagonal tile, and two opposed triangular tiles defined by adjacent hexagonal tiles on either side of this main tile. As will be appreciated by the skilled artisan, different hexagonal or nestled tile geometries will result in the delineation of different rectangular tile region shapes, as will different boundary profiles (straight vs. curved) will result in the definition of different boundary value statements, defined further below.

Continuing with the illustrated example, in step 1519, the coordinates within associated rectangular tile 1814 are again rescaled, as shown on the axis of FIG. 18B, so that the intersection point’s location, within the associated rectangular tile, is now represented in the rescaled coordinates by a vector d where each of its x and y coordinates are given by:

d_(x) = 2 * (uv_(x) − C_(corner_(x))) − 1

d_(y) = 3 * (uv_(y) − C_(corner_(y))).

Thus, the possible x and y values of the position of intersection point 1411 within associated rectangular tile 1814 are now contained within -1 < x < 1 and 0 < y < 3. This will make the next step easier to compute.

To efficiently find the region encompassing a given intersection point in these rescaled coordinates, the fact that, within the rectangular element 1814, each region is separated by a diagonal line is used. For example, this is illustrated in FIG. 18B, wherein the lower left region 1804 is separated from the middle “inverted house” region 1806 and lower right region 1808 by a downward diagonal line 1855, which in the rescaled coordinates of FIG. 18B, follows the simple equation y = -x. Thus, all points where x < -y are located in the lower left region. Similarly, the lower right region 1808 is separated from the other two regions by a diagonal line 1857 described by the equation y < x. Therefore, in step 1521, the associated region containing the intersection point is evaluated by using these two simple conditional statements. The resulting set of two Boolean values will thus be specific to the region where the intersection point is located. For example, the checks (caseL = x < y, caseR = y < x) will result in the values (caseL = true, caseR = false), (caseL = false, caseR = true) and (caseL = false, caseR = false) for intersection points located in the lower left region 1804, lower right region 1808 and middle region 1806, respectively. One may then convert these Boolean values to floating points values, wherein usually in most programming languages true/false Boolean values are converted into 1.0/0.0 floating point values. Thus, one obtains the set (caseL, caseR) of values of (1.0, 0.0), (0.0, 1.0) or (0.0, 0.0) for each of the described regions above.

To finally obtain the relative coordinates of the hexagonal center associated with the identified region, in step 1523, the set of converted Boolean values may be used as an input to a single floating point vectorial function operable to map each set of these values to a set of xy coordinates of the associated element center. For example, in the described embodiment and as shown in FIG. 18C, one obtains the relative position vectors of each hexagonal center r with the vectorial function:

$\overset{\rightarrow}{r} = \left( {r_{x},r_{y}} \right) = \left( {0.5 + 0.5 \ast \left( {caseR - caseL} \right),\frac{2}{3} - \left( {caseR - caseL} \right)} \right)$

thus, the inputs of (1.0, 0.0), (0.0, 1.0) or (0.0, 0.0) map to the positions (0.0, -⅓), (0.5, ⅔), and (1.0, -⅓), respectively, which corresponds to the shown hexagonal centers 1863, 1865 and 1867 shown in FIG. 18C, respectively, in the rescaled coordinates.

Now back to FIG. 15 , we may proceed with the final step 1525 to translate the relative coordinates obtained above to absolute 3D coordinates with respect to the display or similar (i.e. in mm). First, the coordinates of the hexagonal tile center and the coordinates of the bottom left corner are added to get the position of the hexagonal tile center in the optical layer’s frame of reference. As needed, the process may then scale back the values into absolute units (i.e. mm) and rotate the coordinates back to the original frame of reference with respect to the display to obtain the 3D positions (in mm) of the optical layer element’s center with respect to the display’s frame of reference, which is then fed into step 1116.

The skilled artisan will note that modifications to the above-described method may also be used. For example, the staggered grid shown in FIG. 17A may be translated higher by a value of ⅓ (in normalized units) so that within each rectangle the diagonals separating each region are located on the upper left and right corners instead. The same general principles described above still applies in this case, and the skilled technician will understand the minimal changes to the equations given above will be needed to proceed in such a fashion. Furthermore, as noted above, different LFSL element geometries can result in the delineation of different (normalized) rectangular tile regions, and thus, the formation of corresponding conditional boundary statements and resulting binary/Boolean region-identifying and center-locating coordinate systems/functions.

In yet other embodiments, wherein a rectangular and/or square microlens array is used instead of a nestled (hexagonal) array, a slightly different method may be used to identify the associated LFSL element (microlens) center (step 1114). Herein, the microlens array is represented by an array of rectangular and/or square tiles. The method, as previously described, goes through step 1515, where the x and y coordinates are rescaled (normalized) with respect to a microlens x and y dimension (henceforth giving each rectangular and/or square tile a width and height of 1 unit). However, at step 1517, the floor() function is used directly on each x and y coordinates of

$\overset{\rightarrow}{uv}$

(the position vector of intersection point 1411) to find the coordinates of the bottom left corner associated with the corresponding square/rectangular tile. Therefrom, the relative coordinates of the tile center from the bottom left corner are added directly to obtain the final scaled position vector:

$\overset{\rightarrow}{r} = \left( {r_{x},r_{y}} \right) = \left( {floor\left( {uv_{x}} \right) + 0.5,\mspace{6mu} floor\left( {uv_{y}} \right) + 0.5} \right)$

Once this vector is known, the method goes directly to step 1525 where the coordinates are scaled back into absolute units (i.e. mm) and rotated back to the original frame of reference with respect to the display to obtain the 3D positions (in mm) of the optical layer element’s center with respect to the display’s frame of reference, which is then fed into step 1116.

The light field rendering methods described above (from FIGS. 11 to 20D) may also be applied, in some embodiments, at a subpixel level in order to achieve an improved light field image resolution. Indeed, a single pixel on a color subpixelated display is typically made of several color primaries, typically three colored elements - ordered (on various displays) either as blue, green and red (BGR) or as red, green and blue (RGB). Some displays have more than three primaries such as the combination of red, green, blue and yellow (RGBY) or red, green, blue and white (RGBW), or even red, green, blue, yellow and cyan (RGBYC). Subpixel rendering operates by using the subpixels as approximately equal brightness pixels perceived by the luminance channel. This allows the subpixels to serve as sampled image reconstruction points as opposed to using the combined subpixels as part of a “true” pixel. For the light field rendering methods as described above, this means that the center position of a given pixel (e.g. pixel 1401 in FIG. 14 ) is replaced by the center positions of each of its subpixel elements. Therefore, the number of color samples to be extracted is multiplied by the number of subpixels per pixel in the digital display. The methods may then follow the same steps as described above and extract the associated image portions of each subpixel individually (sequentially or in parallel).

In FIG. 21A, an exemplary pixel 2115 is comprised of three RBG subpixels (2130 for red, 2133 for green and 2135 for blue). Other embodiments may deviate from this color partitioning, without limitation. When rendering per pixel, as described in FIG. 11 or in FIG. 19 , the image portion 2145 associated with said pixel 2115 is sampled to extract the luminance value of each RGB color channels 2157, which are then all rendered by the pixel at the same time. In the case of subpixel rendering, as illustrated in FIG. 21B, the methods find the image portion 2147 associated with blue subpixel 2135. Therefore, only the subpixel channel intensity value of RGB color channels 2157 corresponding to the target subpixel 2135 is used when rendering (herein the blue subpixel color value, the other two values are discarded). In doing so, a higher adjusted image resolution may be achieved for instance, by adjusting adjusted image pixel colours on a subpixel basis, and also optionally discarding or reducing an impact of subpixels deemed not to intersect or to only marginally intersect with the user’s pupil.

To further illustrate embodiments making use of subpixel rendering, with reference to FIGS. 22A and 22B, a (LCD) pixel array 2200 is schematically illustrated to be composed of an array of display pixels 2202 each comprising red (R) 2204, green (G) 2206, and blue (B) 2208 subpixels. As with the examples provided above, to produce a light field display, a light field shaping layer, such as a microlens array, is to be aligned to overlay these pixels such that a corresponding subset of these pixels can be used to predictably produce respective light field rays to be computed and adjusted in providing a corrected image. To do so, the light field ray ultimately produced by each pixel can be calculated knowing a location of the pixel (e.g. x,y coordinate on the screen), a location of a corresponding light field element through which light emanating from the pixel will travel to reach the user’s eye(s), and optical characteristics of that light field element, for example. Based on those calculations, the image correction algorithm will compute which pixels to light and how, and output subpixel lighting parameters (e.g. R, G and B values) accordingly. As noted above, to reduce computation load, only those pixels producing rays that will interface with the user’s eyes or pupils may be considered, for instance, using a complementary eye tracking engine and hardware, though other embodiments may nonetheless process all pixels to provide greater buffer zones and/or a better user experience.

In the example shown in FIG. 22A, an angular edge 2209 is being rendered that crosses the surfaces of affected pixels 2210, 2212, 2214 and 2216. Using standard pixel rendering, each affected pixel is either turned on or off, which to some extent dictates a relative smoothness of the angular edge 2209.

In the example shown in FIG. 22B, subpixel rendering is instead favoured, whereby the red subpixel in pixel 2210, the red and green subpixels in pixel 2214 and the red subpixel in pixel 2216 are deliberately set to zero (0) to produce a smoother representation of the angular edge 2209 at the expense of colour trueness along that edge, which will not be perceptible to the human eye given the scale at which these modifications are being applied. Accordingly, image correction can benefit from greater subpixel control while delivering sharper images.

In order to implement subpixel rendering in the context of light field image correction, in some embodiments, ray tracing calculations must be executed in respect of each subpixel, as opposed to in respect of each pixel as a whole, based on a location (x,y coordinates on the screen) of each subpixel. Beyond providing for greater rendering accuracy and sharpness, subpixel control and ray tracing computations may accommodate different subpixel configurations, for example, where subpixel mixing or overlap is invoked to increase a perceived resolution of a high resolution screen and/or where nonuniform subpixel arrangements are provided or relied upon in different digital display technologies.

In some embodiments, however, in order to avoid or reduce a computation load increase imparted by the distinct consideration of each subpixel, some computation efficiencies may be leveraged by taking into account the regular subpixel distribution from pixel to pixel, or in the context of subpixel sharing and/or overlap, for certain pixel groups, lines, columns, etc. With reference to FIG. 23 , a given pixel 2300, much as those illustrated in FIGS. 22A and 22B, is shown to include horizontally distributed red (R) 2304, green (G) 2306, and blue (B) 2308 subpixels. Using standard pixel rendering and ray tracing, light emanating from this pixel can more or less be considered to emanate from a point located at the geometric center 2310 of the pixel 2300. To implement subpixel rendering, ray tracing could otherwise be calculated in triplicate by specifically addressing the geometric location of each subpixel. Knowing the distribution of subpixels within each pixel, however, calculations can be simplified by maintaining pixel-centered computations and applying appropriate offsets given known geometric subpixel offsets (i.e. negative horizontal offset 2314 for the red subpixel 2304, a zero offset for the green 2306 and a positive horizontal offset 2318 for the blue subpixel 2308). In doing so, light field image correction can still benefit from subpixel processing without significantly increased computation load.

While this example contemplates a linear (horizontal) subpixel distribution, other 2D distributions may also be considered without departing from the general scope and nature of the present disclosure. For example, for a given digital display screen and pixel and subpixel distribution, different subpixel mappings can be determined to define respective pixel subcoordinate systems that, when applied to standard pixel-centric ray tracing and image correction algorithms, can allow for subpixel processing and increase image correction resolution and sharpness without undue processing load increases.

In some embodiments, additional efficiencies may be leveraged on the GPU by storing the image data, for example image 1306, in the GPU’s texture memory. Texture memory is cached on chip and in some situations is operable to provide higher effective bandwidth by reducing memory requests to off-chip DRAM. Specifically, texture caches are designed for graphics applications where memory access patterns exhibit a great deal of spatial locality, which is the case of the steps 1110-1126 of method 1100. For example, in method 1100, image 1306 may be stored inside the texture memory of the GPU, which then greatly improves the retrieval speed during step 1126 where the color channel associated with the portion of image 1306 at intersection point 1423 is determined.

With reference to FIGS. 28 to 29C, and in accordance with different embodiments, different illustrations and plots are shown illustrating the impact certain parameters may have on the performance of a light field display’s perceived resolution (herein defined as the size of the smallest resolvable point size or SRPS). In these examples, an image of a vertical and horizontal black and white striped pattern (one example of which is shown in FIG. 28 ) was created and displayed on the light field display. At first, the striped patterns featured linewidths in the range of 1 pixel to 20 pixels while another had linewidths ranging from 1 to 100 pixels at twice the resolution (to increase the granularity of the test results). A Nikon DSLR camera with 45 mm lens and manufactured entrance pupil was used to take images (of the light field image) to best simulate the depth of field and focus capability of the human eye. Both the light field display and the camera were placed on an active levelling optical bench to prevent distortion from the vibrations in the building. All of the following tests were done using MLA #2 of table 2 above (e.g. 65 mm focal length and 1 mm pitch) with the display #1 from table 1 (e.g. 4 K Sony™ Xperia™ XZ Premium phone display). Unless indicated otherwise, rendering software placed the virtual image at 6 m behind the display and the viewing distance is 65 cm, perpendicular to the light field display. The images were analyzed qualitatively and a SRPS value was determined based on which striped pattern had discernable dark and light striped patterns without interruption to the stripes. The compound lens on the camera had greater depth of field that a human eye would, thus for areas where diopter change occurs quickly (virtual image closer to the camera than the display) the results were biased towards lower resolution than a human eye would perceive them. The change in SRPS as a function of different parameters were then plotted in FIGS. 29A to 29D, as will be explained below.

It was generally observed that the vertical SRPS is lower than the horizontal SRPS. This asymmetry is believed to be caused by a limitation of the display’s drivers that limited subpixel rendering control in the vertical direction. For example, for the vertical orientation, it was found that it takes roughly 5-6 pixel-width lines, meaning a SRPS of roughly 0.25 mm for a clearly discernible pattern to be formed. In comparison the human eye resolution is about 0.016 degrees which at 65 cm gives a SRPS of around 0.2 mm. In the presently discussed example, the horizontal SRPS is better (i.e. smaller) due to better subpixel control and discernable patterns may be seen for lines 3-4 pixels apart. This would give an effective SRPS of roughly 0.2 mm or approximately average human eye resolution at a 65 cm viewing distance.

Now with reference to FIG. 29A, the change in SRPS in both horizontal and vertical directions are plotted as a function of viewing distance. We see that for distances of 35 cm and above, the closer the user is to the display the smaller the SRPS is in both directions. However, the rate of increase in SRPS at larger distances is small which may be construed as the light field display having a relatively high tolerance for changes in the user viewing distance.

Similarly, FIG. 29B shows a plot illustrating the change in SRPS (in mm) in the horizontal and vertical orientation as a function of the virtual image distance. This distance is herein measured as a diopter change from 65 cm, in which case 0 diopters is (a flat image). The observed SRPS in both orientations is smallest within the 1-1.4 diopter range (which includes the distance of 6 m as used above or larger towards infinity).

FIG. 29C shows a plot illustrating the change in SRPS (in mm) in the horizontal and vertical orientation as a function of the viewing angle. In this example, the viewing distance from the display in the z-direction is kept fixed at 65 cm at the virtual image was placed at infinity. The reference viewing angle is the user facing the display thus the eye plane is perpendicular or at 90 degrees. It can be seen that the optimal field of view (FOV) is around 30 degrees from this reference angle and that a usable FOV (not optimal but still usable) is around 60 degrees.

While the present disclosure describes various exemplary embodiments, the disclosure is not so limited. To the contrary, the disclosure is intended to cover various modifications and equivalent arrangements included within the general scope of the present disclosure. 

What is claimed is:
 1. A digital display device to render an input image for viewing by a viewer having reduced visual acuity, the device comprising: a digital display medium comprising an array of pixels and operable to render a pixelated image accordingly; a microlens array disposed relative to said digital display medium so to dispose each microlens of the microlens array over an underlying set of said pixels to shape a light field emanating therefrom and thereby at least partially govern a projection thereof from said digital display medium toward the viewer; and a hardware processor operable on pixel data for the input image to output adjusted image pixel data to be rendered via said digital display medium and projected through said microlens array in accordance with a stored alignment thereof so to produce a designated image perception adjustment to at least partially address the viewer’s reduced visual acuity; wherein a dimension of each microlens is selected to minimize a spot size on a retina of the viewer produced by said underlying set of said pixels.
 2. The digital display device of claim 1, wherein said hardware processor is operable to: digitally map the input image on an adjusted image plane designated to provide the viewer with said designated image perception adjustment; associate said adjusted image pixel data with at least some of said pixel sets according to said mapping; and render said adjusted image pixel data via said pixel sets thereby rendering a perceptively adjusted version of the input image when viewed through said microlens array.
 3. The digital display device of claim 2, wherein said adjusted image plane is a virtual image plane virtually positioned relative to said digital display medium at a designated minimum viewing distance designated such that said perceptively adjusted version of the input image is adjusted to accommodate the viewer’s reduced visual acuity.
 4. The digital display device of claim 2, wherein said adjusted image plane is designated as a user retinal plane, wherein said mapping is implemented by scaling the input image on said user retinal plane as a function of an input user eye focus aberration parameter.
 5. The digital display device of claim 1, wherein a diameter of each microlens is selected to correspond with a dimension of about 3 to about 15 of said pixels.
 6. The digital display device of claim 1, wherein a diameter of each microlens is selected to correspond with a dimension of about 3 to about 10 of said pixels.
 7. The digital display device of claim 1, wherein a diameter of each microlens is selected to correspond with a dimension of about 5 to about 10 of said pixels.
 8. The digital display device of claim 1, wherein said dimension of each microlens is selected to minimize said spot size on the retina of the viewer produced by each of a set of constituent subpixels for each of said underlying set of said pixels.
 9. The digital display device of claim 1, wherein a diameter of each microlens is selected to correspond with a dimension of about 10 to about 35 of said pixels.
 10. The digital display device of claim 1, wherein a diameter of each microlens is selected to correspond with a dimension of about 15 to 25 of said pixels.
 11. The digital display device of claim 1, wherein said microlens array is disposed at a designated distance from said digital display medium that is shorter than a focal length of said microlens array so to produce a divergent light field therefrom.
 12. The digital display device of claim 11, wherein said designated distance is selected such that said microlens array focuses on a virtual image plane generated thereby.
 13. A microlens array for use with a digital display medium comprising an array of pixels and operable to render a pixelated image accordingly to be viewed by a viewer having a reduced visual acuity, wherein a microlens array is dimensioned to be disposed relative to the digital display medium and comprises an array of microlenses, each one of which being disposed, when overlaid onto the digital display medium, to be centered over a corresponding set of the pixels to shape a light field emanating therefrom and thereby at least partially govern a projection thereof from said digital display medium toward the viewer, wherein a dimension of each microlens is selected to minimize a spot size on a retina of the viewer produced by given pixels of said corresponding set of the pixels.
 14. The microlens array of claim 13, wherein a diameter of each microlens is selected to correspond with a dimension of about 3 to about 15 of said pixels.
 15. The microlens array of claim 13, wherein a diameter of each microlens is selected to correspond with a dimension of about 3 to about 10 of said pixels.
 16. The microlens array of claim 13, wherein a diameter of each microlens is selected to correspond with a dimension of about 5 to about 10 of said pixels.
 17. The microlens array of claim 13, wherein a diameter of each microlens is selected to correspond with a dimension of about 10 to about 35 of said pixels.
 18. The microlens array of claim 13, wherein a diameter of each microlens is selected to correspond with a dimension of about 15 to 25 of said pixels. 